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Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2019	Mar. 20, 2020	Sep. 30, 2019
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-39049
Entity Registrant Name	EXAGEN INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0434866
Entity Central Index Key	0001274737
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Address, Address Line One	1261 Liberty Way,
Entity Address, Address Line Two	Suite C
Entity Address, City or Town	Vista
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92081
City Area Code	(760)
Local Phone Number	560-1501
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	XGN
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Public Float			$ 104,900,000
Documents Incorporated by Reference	Certain information required to be disclosed in Part III of this report is incorporated by reference from the registrant's definitive Proxy Statement for the 2020 Annual Meeting of Stockholders, which proxy statement will be filed not later than 120 days after the end of the fiscal year covered by this Form 10-K.
Entity Common Stock, Shares Outstanding		12,627,056

Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 72,084	$ 13,164
Accounts receivable, net	5,715	5,952
Prepaid expenses and other current assets	3,451	2,196
Total current assets	81,250	21,312
Property and equipment, net	1,380	1,566
Goodwill	5,506	5,506
Other assets	174	503
Total assets	88,310	28,887
Current liabilities:
Accounts payable	1,476	1,279
Accrued liabilities	4,419	3,923
Proceeds received prior to issuance of Series G redeemable convertible preferred stock	0	3,750
Total current liabilities	5,895	8,952
Borrowings-non-current portion, net of discounts and debt issuance costs	25,854	24,617
Redeemable convertible preferred stock warrant liabilities	0	1,503
Deferred taxes	264	245
Other non-current liabilities	638	304
Total liabilities	32,651	35,621
Commitments and contingencies (Note 6)
Redeemable convertible preferred stock	0	105,232
Stockholders' equity (deficit):
Preferred stock	0	0
Common stock	13	0
Additional paid-in capital	220,248	40,598
Accumulated deficit	(164,602)	(152,564)
Total stockholders' equity (deficit)	55,659	(111,966)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$ 88,310	$ 28,887

Unaudited Condensed Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 40,387	$ 32,440
Operating expenses:
Costs of revenue (excluding amortization of purchased technology)	18,808	15,379
Selling, general and administrative expenses	28,702	19,675
Research and development expenses	2,176	2,125
Amortization of intangible assets	0	141
Total operating expenses	49,686	37,320
Loss from operations	(9,299)	(4,880)
Interest expense	(3,491)	(2,868)
Change in fair value of financial instruments	267	(318)
Other income, net	510	112
Loss before income taxes	(12,013)	(7,954)
Income tax expense	25	58
Net loss	(12,038)	(8,012)
Accretion of redeemable convertible preferred stock	(4,640)	(9,318)
Deemed dividend recorded in connection with financing transactions	(13,601)	(1,152)
Net loss attributable to common stockholders (diluted)	$ (30,279)	$ (18,482)
Net loss per share:
Net loss per share, basic and diluted (USD per share)	$ (8.46)	$ (293.34)
Weighted average shares:
Weighted-average number of shares used to compute net loss per share, basic and diluted (in shares)	3,578,771	63,005

Unaudited Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Series H redeemable convertible preferred stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017	497,691,757
Beginning balance at Dec. 31, 2017	$ 92,046
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock	$ 9,318
Issuance of Series redeemable convertible preferred stock for aggregate proceeds, net of issuance costs (in shares)	34,914,327
Issuance of Series redeemable convertible preferred stock for aggregate proceeds, net of issuance costs	$ 3,868
Deemed dividend recognized on beneficial conversion features of Series H redeemable convertible preferred stock (Note 8)		$ 0
Ending balance (in shares) at Dec. 31, 2018	532,606,084
Ending balance at Dec. 31, 2018	$ 105,232
Beginning balance (in shares) at Dec. 31, 2017			63,005
Beginning balance at Dec. 31, 2017	(96,684)		$ 0	$ 50,954	$ (147,638)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of redeemable convertible preferred stock	(9,318)			(9,318)
Stock-based compensation	114			114
Issuance of Series redeemable convertible preferred stock for aggregate proceeds of $____ per share, net of issuance costs of $___ (Note 8)	(1,152)			(1,152)
Net loss	$ (8,012)				(8,012)
Ending balance (in shares) at Dec. 31, 2018	63,005		63,005
Ending balance at Dec. 31, 2018	$ (111,966)		$ 0	40,598	(152,564)
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock	$ 4,640
Issuance of Series redeemable convertible preferred stock for aggregate proceeds, net of issuance costs (in shares)	148,928,337	233,446,519
Issuance of Series redeemable convertible preferred stock for aggregate proceeds, net of issuance costs	$ 11,492	$ 3,941
Deemed dividend recognized on beneficial conversion features of Series H redeemable convertible preferred stock (Note 8)	$ 6,741	$ 6,741
Deemed dividend from conversion of Series G to Series H redeemable convertible preferred stock (Note 8) (in shares)	97,592,739
Deemed Dividend	$ 6,860
Conversion of preferred stock to common stock in connection with initial public offering (in shares)	(1,012,573,679)
Conversion of preferred stock to common stock in connection with initial public offering	$ (138,906)
Ending balance (in shares) at Dec. 31, 2019	0
Ending balance at Dec. 31, 2019	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of redeemable convertible preferred stock	$ (4,640)			(4,640)
Exercise of stock options (in Shares)	1,548		1,548
Exercise of stock options	$ 4			4
Stock-based compensation	572			572
Issuance of Series redeemable convertible preferred stock for aggregate proceeds of $____ per share, net of issuance costs of $___ (Note 8)	6,741			6,741
Deemed dividend recognized on beneficial conversion features of Series H redeemable convertible preferred stock	(6,741)			(6,741)
Deemed dividend from conversion of Series G to Series H redeemable convertible preferred stock	(6,860)			(6,860)
Stock issued upon conversion of redeemable convertible preferred shares (in shares)			7,816,643
Conversion of preferred stock to common stock in connection with initial public offering (Note 8)	138,906		$ 8	138,898
Issuance of common stock in initial public offering, net of underwriting discount, commissions and issuance costs (Note 9) (in shares)			4,140,000
Issuance of common stock in initial public offering, net of underwriting discount, commissions and issuance costs (Note 9)	50,444		$ 4	50,440
Net exercise of common stock warrants (in shares)			539,794
Net exercise of common and preferred stock warrants	511		$ 1	510
Reclassification of redeemable convertible preferred stock warrant liabilities as equity	726			726
Net loss	$ (12,038)				(12,038)
Ending balance (in shares) at Dec. 31, 2019	12,560,990		12,560,990
Ending balance at Dec. 31, 2019	$ 55,659		$ 13	$ 220,248	$ (164,602)

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (12,038)	$ (8,012)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	591	731
Amortization of debt discount and debt issuance costs	691	587
Non-cash interest expense	546	515
Revaluation of warrant liabilities	(267)	318
Deferred income taxes	0	31
Loss on disposal of assets	20	6
Stock-based compensation	572	114
Changes in assets and liabilities:
Accounts receivable, net	237	(2,262)
Prepaid expenses and other current assets	(1,255)	(781)
Other assets	(24)	(8)
Accounts payable	528	(824)
Accrued and other liabilities	688	284
Net cash used in operating activities	(9,711)	(9,301)
Cash flows from investing activities:
Purchases of property and equipment	(403)	(199)
Proceeds from sale of property and equipment	300	0
Purchases of short-term investments	0	(2,000)
Maturities of short-term investments	0	2,000
Net cash used in investing activities	(103)	(199)
Cash flows from financing activities:
Proceeds from sale of common stock upon exercise of stock options	4	0
Principal payment on capital lease obligations	(138)	(38)
Proceeds from issuance of 2017 Term Loan, net of issuance costs of $5	0	4,995
Proceeds from initial public offering, net of issuance costs and offering costs	50,444	0
Net cash provided by financing activities	68,734	11,423
Increase in cash, cash equivalents and restricted cash	58,920	1,923
Cash, cash equivalents and restricted cash, beginning of period	13,264	11,341
Cash, cash equivalents and restricted cash, end of period	72,184	13,264
Supplemental disclosure of cash flow information:
Cash paid for interest expense	2,288	1,730
Supplemental disclosure of non-cash items:
Accretion to redemption value of redeemable convertible preferred stock	4,640	9,318
Equipment purchased under capital lease obligations	654	289
Fair value of warrant liabilities recorded as discount on debt	0	289
Costs incurred, but not paid, in connection with capital expenditures	0	331
Conversion of redeemable convertible preferred stock	138,906	0
Net exercise of common and preferred stock warrants	511	0
Issuance costs included in accounts payable and accrued liabilities	0	355
Reclassification of redeemable convertible preferred stock warrant liabilities as equity	726	0
Deemed dividend recognized for beneficial conversion features of Series H redeemable convertible preferred stock	6,741
Adjustment upon adoption of ASC 606	0	3,086
Series F redeemable convertible preferred stock
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	0	2,716
Supplemental disclosure of non-cash items:
Deemed dividend from issuance of Series F redeemable convertible preferred stock	0	1,152
Series G redeemable convertible preferred stock
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	7,742	3,750
Supplemental disclosure of non-cash items:
Deemed dividend from conversion of Series G to Series H redeemable convertible preferred stock	6,860	0
Conversion of Series G to Series H redeemable convertible preferred stock	11,875	0
Series H redeemable convertible preferred stock
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	10,682	0
Supplemental disclosure of non-cash items:
Deemed dividend recognized for beneficial conversion features of Series H redeemable convertible preferred stock	$ 6,741	$ 0

Unaudited Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Series F redeemable convertible preferred stock
Sale of temporary equity, price per share (in dollars per share)		$ 0.078
Issuance costs		$ 7
Series G redeemable convertible preferred stock
Sale of temporary equity, price per share (in dollars per share)	$ 0.078
Issuance costs	$ 124
Series H redeemable convertible preferred stock
Sale of temporary equity, price per share (in dollars per share)	$ 0.047
Issuance costs	$ 318

Condensed Balance Sheets - (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Convertible preferred stock
Shares outstanding (in shares)	0	532,606,084
Preferred stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	10,000,000	0
Shares issued (in shares)	0	0
Shares outstanding (in shares)	0	0
Common stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	200,000,000	1,470,000,000
Shares issued (in shares)	12,560,990	63,005
Shares outstanding (in shares)	12,560,990	63,005
Redeemable Convertible Preferred Stock
Convertible preferred stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	750,300,000	750,300,000
Shares outstanding (in shares)		532,606,084
Liquidation preference	$ 0	$ 163,316
Shares issued (in shares)	0

Statement of Cash Flows (Parenthetical) $ in Thousands	12 Months Ended
Statement of Cash Flows (Parenthetical) $ in Thousands	Dec. 31, 2018 USD ($)
Statement of Cash Flows [Abstract]
Payments of debt issuance costs	$ 5

Organization - (Notes)	12 Months Ended
Organization - (Notes)	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Description of Business Exagen Inc. (the Company) was incorporated under the laws of the state of New Mexico in 2002, under the name Exagen Corporation. In 2003, Exagen Corporation changed its state of incorporation from New Mexico to Delaware by merging with and into Exagen Diagnostics, Inc., pursuant to which the Company changed its name to Exagen Diagnostics, Inc. In January 2019, the Company changed its name to Exagen Inc. The Company is dedicated to transforming the care continuum for patients suffering from debilitating and chronic autoimmune diseases by enabling timely differential diagnosis and optimizing therapeutic intervention. Initial Public Offering On September 23, 2019, the Company closed its initial public offering (the IPO) of 4,140,000 shares of its common stock at a price to the public of $14.00 per share, including the exercise in full by the underwriters of their option to purchase 540,000 additional shares of the Company's common stock. Including the exercise of the option to purchase additional shares, the aggregate net proceeds to the Company from the offering was approximately $50.4 million, net of underwriting discounts, commissions and other offering expenses, for aggregate expenses of approximately $7.5 million. In addition, an aggregate of 7,816,643 shares of common stock, excluding warrant conversions, were issued to the holders of the Company's Series A-3, Series B-3, Series C, Series D, Series E, Series F and Series H redeemable convertible preferred stockholders upon the automatic conversion of all shares of redeemable convertible preferred stock to common stock. Reverse Stock Split On September 6, 2019, the Company effected a one-for-183.635 reverse stock split of its common stock (the Reverse Stock Split). The par value and the authorized shares of the common stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock and the conversion ratio of the redeemable convertible preferred stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented in the accompanying financial statements and notes to the financial statements. Liquidity The Company has suffered recurring losses and negative cash flows from operating activities since inception. The Company anticipates that it will continue to incur net losses into the foreseeable future. At December 31, 2019, the Company had cash and cash equivalents of $72.1 million and had an accumulated deficit of $164.6 million, respectively. Since inception, the Company has financed its operations primarily through private placements of preferred securities, the sale of common stock through its IPO and debt financing arrangements. Based on the Company's current business plan, management believes that its existing capital resources will be sufficient to fund the Company's obligations for at least twelve months following the issuance of these financial statements. To execute its business plans, the Company may need additional funding to support its continuing operations and pursue its growth strategy. Until such time as the Company can achieve significant cash flows from operations, if ever, it expects to finance its operations through the sale of its stock, debt financings or other strategic transactions. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing on terms acceptable to the Company, if at all. The terms of any financing may adversely affect the holdings or the rights of the Company's stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its programs, product portfolio expansion plans or commercialization efforts, which could have a material adverse effect on the Company's business, operating results and financial condition and the Company's ability to achieve its intended business objectives.

Summary Of Significant Accounting Policies - (Notes)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary Of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Basis of Presentation and Use of Estimates

The Company's financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). The preparation of the accompanying financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. Actual results could materially differ from those estimates.

Significant estimates and assumptions made in the accompanying financial statements include, but are not limited to revenue recognition, the fair value of financial instruments measured at fair value, the recoverability of its long-lived assets (including goodwill), net deferred tax assets (and related valuation allowance), and for periods prior to the IPO, the fair value of the Company's common stock and redeemable convertible preferred stock. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Concentration of Credit Risk and Other Risk and Uncertainties

Financial instruments that potentially subject the Company to credit risk consist principally of cash, cash equivalents, and accounts receivable. Substantially all the Company's cash and cash equivalents are held at one financial institution that management believes is of high credit quality. Such deposits may, at times, exceed federally insured limits.

Significant payers are those which represent more than 10% of the Company's total revenue or accounts receivable balance at each respective balance sheet date. For each significant payer, revenue as a percentage of total revenue and accounts receivable as a percentage of total accounts receivable are as follows:


	Revenue
		Years Ended December 31,
		2019		2018
Medicare		25	%	30	%
Blue Shield		12	%	14	%
United Healthcare		11	%	12	%
Medicare Advantage		11	%	10	%
Janssen (SIMPONI^®)		*		*



*						Less than 10%.


	Accounts Receivable
	December 31,
	2019		2018
Medicare	*		26	%
Blue Shield	15	%	16	%
United Healthcare	22	%	11	%
Medicare Advantage	*		11	%
Janssen (SIMPONI^®)	19	%	*



*						Less than 10%.

For the years ended December 31, 2019 and 2018, approximately 82% of the Company's revenue was related to the AVISE^® CTD test.

The Company is dependent on key suppliers for certain laboratory materials. For the years ended December 31, 2019 and 2018, approximately 97% and 95%, respectively, of the Company's inventories were purchased from two suppliers. An interruption in the supply of these materials would impact the Company's ability to perform testing services.

Disaggregation of Revenue

The following table includes the Company's revenues as disaggregated by payer category (in thousands):


	Years Ended December 31,
	2019		2018
Revenue:
Healthcare insurers	$	23,984	$	21,070
Government	9,896		10,024
Client	4,392		608
Other(1)	639		738
Janssen (SIMPONI^®)	1,476		—
Total revenue	$	40,387	$	32,440

(1)Includes patient self-pay that is immaterial.

Fair Value Measurements

The carrying value of the Company's cash and cash equivalents, other assets and accrued liabilities approximate fair value due to the short-term nature of these items. Based on the borrowing rates currently available to the Company for debt with similar terms and consideration of default and credit risk, the carrying value of the Company's long-term borrowings approximates its fair value, which is considered a Level 2 input.

Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs.

The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows:

Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities;

Level 2 - Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level 3 - Unobservable inputs that are supported by little or no market activity for the related assets or liabilities.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Prior to the IPO, the Company's redeemable convertible preferred stock warrant liabilities were measured at fair value on a recurring basis and were classified as Level 3 liabilities. The Company recorded subsequent adjustments to reflect the increase or decrease in estimated fair value at each reporting date in current period earnings.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly-liquid investments purchased with a remaining maturity date upon acquisition of three months or less to be cash equivalents and are stated at cost, which approximates fair value.

In 2016, the Company entered into an arrangement with a financial institution with which it has an existing banking relationship whereby in exchange for the issuance of corporate credit cards, the Company agreed to obtain a $0.1 million certificate of deposit with this financial institution as collateral for the balances borrowed on these credit cards. The Company has classified the value of this certificate of deposit (including all interest earned thereon) within other assets in the accompanying balance sheets. The Company has the right to terminate the credit card program at any time. Upon termination of the credit card program and repayment of all outstanding balances owed, the Company may redeem the certificate of deposit (and all interest earned thereon).

Cash, cash equivalents and restricted cash presented in the accompanying statements of cash flows consist of the following (in thousands):


	December 31,
	2019		2018
Cash and cash equivalents	$	72,084	$	13,164
Restricted cash	100		100
	$	72,184	$	13,264

Property and Equipment

Property and equipment are stated at cost, net of depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of the estimated useful life or the remaining term of the related lease. Maintenance and repairs are charged to expense as incurred, and improvements and betterments are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in other income or expense in the statements of operations in the period realized.

Long-lived Assets

The Company’s long-lived assets are comprised principally of its property and equipment, finite lived intangible assets, and goodwill.

If the Company identifies a change in the circumstances related to its long-lived assets, such as property and equipment and intangible assets (other than goodwill), that indicates the carrying value of any such asset may not be recoverable, the Company will perform an impairment analysis. A long-lived asset (other than goodwill) is deemed to be impaired when the undiscounted cash flows expected to be generated by the asset (or asset group) are less than the asset’s carrying amount. Any required impairment loss would be measured as the amount by which the asset’s carrying value exceeds its fair value, and would be recorded as a reduction in the carrying value of the related asset and a charge to operating expense.

Goodwill is reviewed for impairment annually (during the fourth quarter) or more frequently if indicators of impairment exist. As the Company operates in a single operating segment and reporting unit, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a quantitative assessment. If, after assessing qualitative factors, the Company determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing a quantitative assessment is unnecessary. If deemed necessary, a quantitative assessment compares the fair value of the reporting unit with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired; otherwise, an impairment loss is recorded. There was no indication of impairment of goodwill for any periods presented.

Clinical Studies

From time to time, the Company engages in efforts to scientifically measure and document the application and efficacy of its various testing products. These arrangements typically require the Company to pay a fee to a third-party scientific investigator (usually a physician or research institution) for each subject enrolled in a clinical study, and the Company accrues expenses associated with these efforts as subjects are enrolled in each study. Expenses associated with clinical study activities are recorded in research and development expenses in the accompanying statement of operations.

Redeemable Convertible Preferred Stock

Prior to the completion of the IPO, the Company had multiple classes of redeemable convertible preferred stock, all of which were classified as temporary equity in the accompanying balance sheet as the redemption of the shares were outside of the Company's control. Redeemable convertible preferred stock which was redeemable on or after a certain date at the option of the holder was accreted to its redemption value from the date of issuance to the earliest redemption date.

In connection with the completion of the IPO in September 2019, all outstanding shares of redeemable convertible preferred stock were automatically converted into an aggregate of 7,816,643 shares of common stock, excluding warrant conversions.

Redeemable Convertible Preferred Stock Warrants

Prior to the completion of the IPO, the Company accounted for its redeemable convertible preferred stock warrants as liabilities based upon the characteristics and provisions of each instrument. The redeemable convertible preferred stock warrants were recorded at their fair value on the date of issuance and were revalued on each subsequent balance sheet date, with fair value changes recognized as increases or reductions in the statements of operations. Upon the completion of the IPO, all remaining outstanding warrants to purchase shares of redeemable convertible preferred stock were automatically converted into warrants to purchase shares of common stock. As such, the warrants no longer require liability accounting and the then fair value of the warrant liability was reclassified into stockholders’ equity.

The Company performed the final remeasurement of the warrant liabilities as of the IPO closing date. See Note 7 for the amounts associated with the fair value measurements and Note 5 for further discussion on the remaining warrants.

Revenue Recognition

Substantially all of the Company's revenue has been derived from sales of its testing products and is primarily comprised of a high volume of relatively low-dollar transactions. The Company primarily markets its testing products to rheumatologists and their physician assistants in the United States. The healthcare professionals who order the Company's testing products and to whom test results are reported are generally not responsible for payment for these products. The parties that pay for these services (the Payers) consist of healthcare insurers, government payers (primarily Medicare and Medicaid), client payers (i.e., hospitals, other laboratories, etc.), and patient self-pay. The Company's service is a single performance obligation that is completed upon the delivery of test results to the prescribing physician which triggers revenue recognition.

Payers are billed at the Company's list price. Net revenues recognized consist of amounts billed net of allowances for differences between amounts billed and the estimated consideration the Company expects to receive from such payers. The process for estimating revenues and the ultimate collection of accounts receivable involves significant judgment and estimation. The Company follows a standard process, which considers historical denial and collection experience, insurance reimbursement policies and other factors, to estimate allowances and implicit price concessions, recording adjustments in the current period as changes in estimates. Further adjustments to the allowances, based on actual receipts, is recorded upon settlement. The transaction price is estimated using an expected value method on a portfolio basis. The Company's portfolios are grouped per payer (i.e. each individual third-party insurance, Medicare, client payers, patient self-pay, etc.) and per test basis.

Collection of the Company's net revenues from payers is normally a function of providing complete and correct billing information to the healthcare insurers and generally occurs within 30 to 90 days of billing. Contracts do not contain significant financing components based on the typical period of time between performance of services and collection of consideration.

The Company early adopted Accounting Standards Codification (ASC) Topic 606, Revenue from Contracts with Customers (Topic 606) as of January 1, 2018 using a cumulative-effect adjustment to the opening balance of accumulated deficit and accounts receivable of $3.1 million.

Janssen Promotion Agreement

In December 2018, the Company entered into a co-promotion agreement with Janssen (the Janssen agreement) to co-promote SIMPONI^® in the United States. The Company is responsible for the costs associated with its salesforce

over the course of such co-promotion. Janssen is responsible for all other aspects of the commercialization of SIMPONI^® under the Janssen agreement. In exchange for the Company's sales and co-promotional services, the Company is entitled to a quarterly tiered promotion fee ranging from $750 to $1,250 per prescription based on the incremental increase in total prescribed units of SIMPONI^® for that quarter over a predetermined baseline. The promotion fee is determined on a sliding rate, ranging from the high hundreds of dollars to the low one thousands per prescribed unit of SIMPONI^®, depending on the number of increased prescriptions, and varies per increased prescription. In addition, during the term of the Janssen agreement, the Company is restricted from promoting any other biologic or Janus kinase inhibitor, or JAK inhibitor, used for treatment of indications covered by the agreement without first obtaining Janssen's written consent.

In September 2019, the Company exercised their option to extend the term of the Janssen agreement to December 31, 2021. Janssen can terminate the agreement at any time for any reason upon 30 days' notice to the Company, and the Company can terminate the agreement for any reason at the end of any calendar quarter upon 30 days' notice to Janssen. Either party may terminate the agreement in the event of the other party's default of any of its material obligations under the agreement if such default remains uncured for a specified period of time following receipt of written notice of such default.

The Company's obligations relating to sales and co-promotion services for SIMPONI^® is a series of single performance obligations since Janssen simultaneously receives and consumes benefits provided by the Company's sales and co-promotional services. The method for measuring progress towards satisfying the performance obligations is based on prescribed units in excess of the contractual baseline at the contractual rate earned per unit since the agreement is cancelable. The Company recognized revenue of approximately $1.5 million during the year ended December 31, 2019. The related expenses for marketing SIMPONI^® are included in selling, general and administrative expenses and are expensed as incurred.

Research and Development

Costs associated with research and development activities are expensed as incurred and include, but are not limited to, personnel-related expenses, including stock-based compensation expense, materials, laboratory supplies, consulting costs, costs associated with setting up and conducting clinical studies and allocated overhead including rent and utilities.

Advertising and Marketing Costs

Costs associated with advertising and marketing activities are expensed as incurred. Total advertising and marketing costs were approximately $1.6 million and $1.4 million for the years ended December 31, 2019 and 2018, respectively, and are included in selling, general and administrative expenses in the accompanying statements of operations.

Shipping and Handling Costs

Costs incurred for shipping and handling are included in costs of revenue in the accompanying statements of operations and totaled approximately $1.4 million and $1.2 million for the years ended December 31, 2019 and 2018, respectively.

Stock-Based Compensation

The Company recognizes compensation expense for all stock-based awards to employees and directors based on the grant-date estimated fair values over the requisite service period of the awards (usually the vesting period) on a straight-line basis. The fair value of stock options is determined using the Black-Scholes-Merton (BSM) option pricing model, which requires management to make certain assumptions regarding a number of complex and subjective variables. Equity award forfeitures are recorded as they occur.

The BSM option pricing model incorporates various estimates, including the fair value of the Company's common stock, expected volatility, expected term and risk-free interest rates. The weighted-average expected term of options was calculated using the simplified method. This decision was based on the lack of relevant historical data due to the Company's limited historical experience. In addition, due to the Company's limited historical data, the estimated volatility incorporates the historical volatility over the expected term of the award of comparable companies whose share prices are publicly available. The risk-free interest rate for periods within the contractual term of the option is

based on the U.S. Treasury yield in effect at the time of grant. The dividend yield was zero, as the Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Upon the effective date of the IPO, the Company began using the closing price of its common stock as the fair value of its common stock on the corresponding date. Prior to the completion of the IPO in September 2019, due to the absence of a public market for the Company's common stock, it was necessary to estimate the fair value of the common stock underlying the Company's stock-based awards when performing fair value calculations using the BSM option pricing model. The fair value of the common stock underlying the Company's stock-based awards was assessed on each grant date by the Company's board of directors (Board of Directors).

Comprehensive Loss

Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from nonowner sources. There have been no items qualifying as other comprehensive loss and, therefore, for all periods presented, the Company's comprehensive loss was the same as its reported net loss.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would adjust the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.

Net Loss Per Share

Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Potentially dilutive common stock equivalents are comprised of redeemable convertible preferred stock, warrants for the purchase of redeemable convertible preferred and common stock and options outstanding under the Company's stock option plans. For the years ended December 31, 2019 and 2018, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as the inclusion of the potentially dilutive securities would be antidilutive.

Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares):


	Years Ended December 31,
	2019	2018
Redeemable convertible preferred stock	—	5,202,940
Warrants to purchase redeemable convertible preferred stock	—	224,493
Warrants to purchase common stock	461,273	934,789
Common stock options	1,375,542	661,180
Total	1,836,815	7,023,402

Segment Reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations as, and manages its business in, one operating segment.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB), or other standard setting bodies and adopted by the Company as of the specified effective date. Under the Jumpstart Our Business Startups Act of 2012 (JOBS Act), the Company meets the definition of an emerging growth company. The Company has elected to use the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption.

In February 2016, the FASB issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842). The new topic supersedes Topic 840, Leases, and increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and requires disclosures of key information about leasing arrangements. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, which provides narrow amendments to clarify how to apply certain aspects of the new lease standard, and ASU 2018-11, Leases: Targeted Improvements, which was issued to provide relief to companies from restating comparative periods. Pursuant to this ASU, in the period of adoption the Company will not restate comparative periods presented in its financial statements. The effective date of this guidance for public companies is for reporting periods beginning after December 15, 2018. As an emerging growth company as defined in the JOBS Act, the Company has elected to delay adoption of this ASU until January 1, 2021. Topic 842 mandates a modified retrospective transition method. The Company intends to adopt the new lease standard using a cumulative effect to accumulated deficit and will elect the package of practical expedients, which among other things will allow the Company to carry forward its historical lease classification. The Company is currently evaluating the impact of Topic 842 on its financial statements.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. This update is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2018-13 on its financial statements.

Other Financial Information - (Notes)

12 Months Ended

Dec. 31, 2019

Other Financial Information [Abstract]

Other Financial Information

Note 3. Other Financial Information

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2019		2018
Diagnostic testing supplies	$	1,427	$	1,174
Prepaid product royalties	123		176
Prepaid maintenance and insurance contracts	1,768		698
Other prepaid assets	133		148
Prepaid and other current assets	$	3,451	$	2,196

Property and Equipment

Property and equipment consist of the following (in thousands):


	December 31,
	2019		2018
Furniture and fixtures	$	25	$	25
Laboratory equipment	2,228		1,855
Computer equipment and software	851		796
Leasehold improvements	424		399
Construction in progress	247		310
Total property and equipment	3,775		3,385
Less: accumulated depreciation and amortization	(2,395)		(1,819)
Property and equipment, net	$	1,380	$	1,566

Depreciation and amortization expense for the years ended December 31, 2019 and 2018, was approximately $0.6 million. At December 31, 2019 and December 31, 2018, the gross book value of assets under capital lease was $0.8 million and $0.4 million, respectively, and is classified in "Laboratory equipment" in the table above.

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):


	December 31,
	2019		2018
Accrued payroll and related expenses	$	2,362	$	2,111
Accrued deferred offering costs	—		355
Accrued interest	145		178
Accrued purchases of goods and services	319		243
Accrued royalties	727		602
Accrued clinical study activity	40		146
Capital lease obligations, current portion	238		81
Other accrued liabilities	588		207
Accrued liabilities	$	4,419	$	3,923

Borrowings - (Notes)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Borrowings

Borrowings2017 Term Loan

In September 2017, the Company executed a term loan agreement (the 2017 Term Loan) with Innovatus Life Sciences Lending Fund I, LP (Innovatus) and borrowed $20.0 million, $17.8 million of which was immediately used to repay the Company's existing loan with Capital Royalty Partners II L.P. and its affiliates. On December 7, 2018, the Company borrowed an additional $5.0 million under the 2017 Term Loan. At December 31, 2019, no additional amounts remain available to borrow under the 2017 Term Loan.

In November 2019, the Company executed the First Amendment to the Loan and Security Agreement (Loan Amendment). The interest rate on all borrowings under the Loan Amendment is 8.5%, of which 2.0% is paid in-kind in the form of additional term loans, or PIK Loans, until December of 2022, after which interest accrues at an annual rate of 8.5%. The Company has estimated the effective interest rate of this loan to be approximately 10%. Accrued interest is due and payable monthly, unless the Company elects to pay PIK interest. The outstanding principal and accrued interest on the Loan Amendment will be repaid in twenty-four equal monthly installments commencing in December 2022. Upon repayment of the final installment under the Loan Amendment, the Company is required to pay an additional fee of $1.0 million. This obligation is being accreted into interest expense over the term of Loan Amendment using the effective interest method. For the years ended December 31, 2019 and 2018, the Company issued PIK Loans totaling $0.5 million.

If the Loan Amendment is prepaid after November 19, 2019, but before November 19, 2020, the Loan Amendment requires a prepayment premium of 3% of the aggregate outstanding principal. The prepayment premium decreases by 1% during each subsequent twelve-month period after November 19, 2020.

The Loan Amendment is collateralized by a first priority security interest on substantially all of the Company's assets, including intellectual property. The affirmative covenants of the Loan Amendment require that the Company timely file taxes, maintain good standing and government compliance, maintain liability and other insurance, provide prompt notification of significant corporate events, and furnish audited financial statements within 150 days of fiscal year end without qualification as to the scope of the audit or as to going concern and without any other similar qualification.

The affirmative covenants require that the Company achieve a specified level of revenue, as measured quarterly on a rolling twelve-month basis, and commencing with the quarter ending December 31, 2019. The consequences of failing to achieve the performance covenant will be waived if, within sixty days of failing to achieve the performance covenant, the Company issues additional equity securities or subordinated debt with net proceeds sufficient to fund any cash flow deficiency generated from operations, as defined. In addition, the Loan Amendment requires that the Company maintain certain levels of minimum liquidity. The Company is required to maintain an unrestricted cash balance of $2.0 million.

The negative covenants provide, among other things, that without the prior consent of Innovatus subject to certain exceptions, the Company may not dispose of certain assets, engage in certain business combinations or acquisitions, incur additional indebtedness or encumber any of the Company's property, pay dividends on the Company's capital stock or make prohibited investments. The Loan Amendment agreement provides that an event of default will occur if, among other triggers, (i) the Company defaults in the payment of any amount payable under the agreement when due, (ii) there occurs any circumstance(s) that could reasonably be expected to result in a material adverse effect on the Company's business, operations or condition, or on the Company's ability to perform its obligations under the agreement, (iii) the Company becomes insolvent, (iv) the Company undergoes a change in control or (v) the Company breaches any negative covenants or certain affirmative covenants in the agreement or, subject to a cure period, otherwise neglects to perform or observe any material item in the agreement.

At December 31, 2019, the Company was in compliance with all covenants of the Loan Amendment.

Upon an event of default in any of the Loan Amendment covenants, the repayment of the Loan Amendment may be accelerated and the applicable interest rate will be increased by 4.0% until the default is cured. Although repayment of the Loan Amendment can be accelerated under certain circumstances, the Company believes acceleration of this loan is not probable as of the date of these financial statements. Accordingly, the Company has reflected the amounts of the Loan Amendment due beyond twelve months of the balance sheet date as non-current.

In connection with the 2017 Term Loan, the Company paid issuance costs of $0.4 million to Innovatus and an additional $0.1 million to third parties. These fees were recorded as discounts to the carrying value of the 2017 Term Loan. The Company also issued Innovatus warrants (i) on the closing date of the 2017 Term Loan, to purchase 15,384,615 shares of Series F redeemable convertible preferred stock at an exercise price of $0.078 per share and (ii) on December 7, 2018, to purchase 3,846,154 shares of Series F redeemable convertible preferred stock at an exercise price of $0.078 per share (Note 5). These warrants are immediately exercisable and will expire if

unexercised seven years after their issuance. The fair value of the warrants on each of their dates of issuance, determined using BSM option pricing model, was recorded as a discount to long-term debt and an offsetting amount recognized as a liability. The resulting debt discount is being amortized to interest expense using the effective interest method over the term of the 2017 Term Loan. In connection with the completion of the IPO in September 2019, the Series F redeemable convertible preferred stock warrants automatically converted into warrants exercisable for an aggregate of 104,722 shares of common stock.

Future Minimum Payments on the Outstanding Borrowings

As of December 31, 2019, future minimum aggregate payments, including interest, for outstanding borrowings under the Loan Amendment are as follows (in thousands):


	Years Ending December 31,

2020	$	1,725
2021	1,755
2022	2,996
2023	15,619
2024	14,280
Total	36,375
Less:
Unamortized debt discount and issuance costs	(390)
Interest	(10,131)
Total borrowings, net of discounts and debt issuance costs	$	25,854

Warrants to Purchase Common or Preferred Stock - (Notes)

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Warrants to Purchase Common or Preferred Stock

In connection with the completion of the Company's IPO in September 2019:

•The remaining outstanding Series F redeemable convertible preferred stock warrants automatically converted into warrants exercisable for an aggregate 104,722 shares of common stock.

•Warrants to purchase common stock for 569,184 shares of the Company's common stock were exercised via cashless exercise resulting in the issuance of 512,363 shares of common stock. Unexercised warrants to purchase common stock for 9,054 shares were terminated prior to the completion of the IPO.

•Warrants to purchase Series D and Series E redeemable convertible preferred stock for 119,771 shares of the Company's common stock were exercised via cashless exercise resulting in the issuance of 27,431 shares of common stock.

Outstanding Warrants

The following warrants to purchase common stock were outstanding as of December 31, 2019:

Exercise Price

Issuance date

Expiration date

Common stock warrants

282,402

1.84

January 19, 2016

January 19, 2026

Common stock warrants

74,018

1.84

March 31, 2016

March 31, 2026

Common stock warrants

131

1.84

April 1, 2016

April 1, 2026

Common stock warrants (1)

83,778

14.32

September 8, 2017

September 8, 2024

Common stock warrants (1)

20,944

14.32

December 7, 2018

December 7, 2025

461,273

(1) Prior to the conversion upon IPO, the remaining warrants were for the purchase of Series F redeemable convertible preferred stock.

The outstanding warrants to purchase shares of common stock are equity classified at December 31, 2019.

Commitment and Contingencies - (Notes)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

As of December 31, 2019, the Company leases an office and laboratory space in Vista, California, under a lease that expires in January 2021, with options to extend the lease for two additional 36-month periods. In addition, the Company also leases an office space in Vista, California, under a lease that expires in January 2021 with an option to extend the lease for an additional 24-month period. The Company's lease payments under each of these leases are subject to escalation clauses.

Minimum annual lease payments under non-cancelable lease arrangements at December 31, 2019 are as follows (in thousands):


Years Ending December 31,	Capital Leases		Operating Leases
2020	$	272	$	411
2021	272		34
2022	246		—
2023	159		—
2024	—		—
Total minimum lease payments	949		$	445
Less: amount representing interest	(75)
Present value of future minimum lease payments	874
Less: current portion	(238)
Long-term capital lease obligations	$	636

For the years ended December 31, 2019 and 2018, rent expense was $0.5 million and $0.4 million, respectively.

Acquisition-related liabilities

In connection with the acquisition of the medical diagnostics division of Cypress Bioscience, Inc. in 2010, the Company was required to pay certain amounts in the event that certain revenue milestones were achieved and upon the first commercial sale of a product associated with this acquisition. The acquisition also included amounts that may be due under several licensing agreements. All milestone payments other than one have been paid as of December 31, 2017. The remaining milestone obligation is for an additional $2.0 million payment due to Prometheus Laboratories, Inc. (Prometheus) for which the fair value was determined to be zero at December 31, 2019 and December 31, 2018.

In addition, the Company has ongoing royalty payment obligations on net sales of products which incorporate certain acquired technologies ranging from 2.5% to 7.5%. Future royalties payable under these arrangements are limited to the lesser of an aggregate of $4.2 million (including an upfront payment of $100,000) or the total royalties earned through January 1, 2024.

Licensing Agreements

The Company has licensed technology for use in its diagnostic tests. In addition to the milestone payments required by these agreements as described above, individual license agreements generally provide for ongoing royalty payments on net sales of products which incorporate licensed technology, as defined, ranging from 3.0% to 20.0%. Royalties are accrued when earned and recorded in costs of revenue in the accompanying statement of operations.

Supply Agreement

In January 2018, the Company entered into a supply agreement with one supplier for reagents which includes a minimum annual purchase commitment of $3.25 million for each of the three years covered by the agreement, which terminates in 2021.

Contingencies

In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications; including subpoenas and other civil investigative demands, from governmental agencies, Medicare or Medicaid payers and managed care organizations reviewing billing practices or requesting comment on allegations of billing irregularities that are brought to their attention through billing audits or third parties. The Company's exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated.

Litigation

The Company is not a party to any litigation and does not have contingent reserves established for any litigation liabilities. From time to time, the Company may be subject to various legal proceedings that arise in the ordinary course of business activities.

Fair Value Measurements - (Notes)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following table sets forth the Company's financial instruments that were measured at fair value on a recurring basis within the fair value hierarchy (in thousands):


	December 31, 2019
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	70,760	$	70,760	$	—	$	—


	December 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	8,618	$	8,618	$	—	$	—
Liabilities:
Redeemable convertible preferred stock warrant liabilities	$	1,503	$	—	$	—	$	1,503

The fair value of the Company's money market funds is based on quoted market prices.

The following table includes a roll-forward of the financial instruments measured on a recurring basis and classified within Level 3 of the fair value hierarchy (in thousands):


	Liability Classified Warrants
Balances at December 31, 2017	$	896
Issuance of warrants to purchase shares of Series F redeemable convertible preferred stock in connection with 2017 Term Loan (Note 4)	289
Remeasurement of financial instruments	318
Balances at December 31, 2018	1,503
Remeasurement of financial instruments	(267)
Net exercise of preferred stock warrants	(510)
Reclassification of liability classified warrants to stockholders' equity (deficit)	(726)
Balance at December 31, 2019	$	—

Changes in the fair value of the Company's liability classified warrants are recorded in the line item change in fair value of financial instruments in the accompanying statement of operations.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Redeemable Convertible Preferred Stock	12 Months Ended
Redeemable Convertible Preferred Stock	Dec. 31, 2019
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock On January 2, 2019, the Company amended and restated its restated certificate of incorporation to, among other things, increase its authorized shares of convertible preferred stock from 750,300,000 to 955,500,000 shares, of which 205,200,000 shares are designated as Series G convertible preferred stock and set forth the rights, preferences and privileges of the Series G convertible preferred stock. On July 11, 2019, the Company amended and restated its restated certificate of incorporation to among other things, increase its authorized shares of convertible preferred stock from 955,500,000 to 1,038,667,059 shares, of which 479,967,595 shares are designated as Series H redeemable convertible preferred stock and set forth the rights, preferences and privileges of the Series H redeemable convertible preferred stock. Upon completion of the Company's IPO in September 2019, an aggregate of 7,816,643 shares of common stock, excluding warrant conversions, were issued to the holders of the Company's Series A-3, Series B-3, Series C, Series D, Series E, Series F and Series H redeemable convertible preferred stockholders upon the automatic conversion of all shares of redeemable convertible preferred stock to common stock. As a result, no shares of redeemable convertible preferred stock remain outstanding at December 31, 2019. Series F Financing In December 2017, the Company's Board of Directors authorized a third tranche closing of the issuance to existing preferred stockholders in connection with the Company's Series F financing, which was completed between December 2017 and January 2018. In December 2017, a group of existing investors of the Company purchased 54,246,756 shares of Series F redeemable convertible preferred stock at a per share price of $0.078 for aggregate gross proceeds of approximately $4.2 million. In early January 2018, a group of existing stockholders of the Company purchased an additional 34,914,327 shares of Series F redeemable convertible preferred stock at a per share price of $0.078 for aggregate gross proceeds of approximately $2.7 million. The Company concluded that the third tranche closing of the Series F preferred stock purchase agreement contained a single freestanding financial instrument, shares of Series F redeemable convertible preferred stock, and the Company determined there were no embedded features requiring bifurcation in the shares of Series F redeemable convertible preferred stock issued in the third tranche closing. The Company accounted for the difference between the estimated fair value and the $0.078 per share purchase price of shares of Series F redeemable convertible preferred stock issued in the third tranche closing as a deemed dividend since all investors in the third closing are existing preferred stockholders of the Company, and the Company did not identify any elements to the transaction which it believes were compensatory in nature. As a result, the Company recognized a deemed dividend in the amount of $1.2 million in the first quarter of 2018, that was recorded as additional paid-in capital (in the absence of retained earnings) in the accompanying statement of redeemable convertible preferred stock and stockholders’ deficit. Series G Financing In January 2019, the Company entered into an agreement with new and certain existing preferred stockholders to issue shares of Series G redeemable convertible preferred stock in multiple separate closings at per share price of $0.078 in each closing. Shares of Series G redeemable convertible preferred stock were issuable under the Series G preferred stock purchase agreement until the earlier of March 31, 2019 or the issuance of all authorized shares of Series G redeemable convertible preferred stock, as specified in the Company's amended and restated certificate of incorporation. In January 2019 and March 2019, the Company sold 88,030,905 and 9,615,384 shares, respectively, of Series G redeemable convertible preferred stock for aggregate gross proceeds of approximately $7.6 million to new and existing investors, of which $3.75 million of gross proceeds were received as of December 31, 2018 and are included in the accompanying December 31, 2018 balance sheet. In May 2019, the Company sold an additional 51,282,048 shares of Series G redeemable convertible preferred stock for aggregate gross proceeds of approximately $4.0 million to existing investors. In addition, in May 2019, the Series G preferred stock purchase agreement was amended to include the right of the Company to require certain holders of Series G redeemable convertible preferred stock to purchase an additional 32,051,280 shares of Series G redeemable convertible preferred stock at $0.078 per share, for total aggregate proceeds of $2.5 million, at any time after July 31, 2019 and prior to May 31, 2020. This right terminated in connection with the issuance of the Series H redeemable convertible stock in July 2019. The Company concluded that the closings of the Series G preferred stock purchase agreement in January and March 2019, contained a single freestanding financial instrument, shares of Series G redeemable convertible preferred stock, and the Company determined there were no embedded features requiring bifurcation in the shares of Series G redeemable convertible preferred stock issued. The Company concluded the closing in May 2019 contained two freestanding financial instruments, shares of Series G redeemable convertible preferred stock and the Company call right, and the Company concluded there were no embedded features requiring bifurcation in the shares of Series G redeemable convertible preferred stock issued. The Company call right was deemed to have nominal value since it was with insiders with knowledge of the imminent closing of Series H redeemable convertible stock. Series H Financing In July 2019, the Company entered into an agreement with a new investor to issue shares of Series H redeemable convertible preferred stock at a per share price of $0.04712. Pursuant to the terms of the agreement, the new investor purchased 233,446,519 shares of Series H redeemable convertible preferred stock for gross proceeds of approximately $11.0 million. In connection with the Series H financing, the Company converted all of the 148,928,337 outstanding shares of the Company's Series G redeemable convertible preferred stock into 246,521,076 shares of Series H redeemable convertible preferred stock on a dollar-for-dollar basis. The Company concluded that the closing of the Series H preferred stock purchase agreement contained a single freestanding financial instrument, shares of Series H redeemable convertible preferred stock, and the Company determined there were no embedded features requiring bifurcation in the shares of Series H redeemable convertible preferred stock issued at closing. The Company accounted for the difference between the effective conversion price of $0.04712 and the fair value of the underlying common stock at the commitment date as a beneficial conversion feature, which was immediately accreted as a deemed dividend. As a result, the Company recognized a beneficial conversion feature in the amount of $6.7 million in the third quarter of 2019, that was recorded as additional paid-in capital (in the absence of retained earnings) in the accompanying statement of redeemable convertible preferred stock and stockholders’ equity (deficit). Additionally, the Company concluded that the conversion of shares of Series G into shares of Series H redeemable convertible preferred stock in connection with the issuance of Series H redeemable convertible preferred stock represented an extinguishment of the Series G shares. As a result, the Company recognized a deemed dividend for the extinguishment charge in the amount of $6.9 million in the third quarter of 2019, that was recorded as additional paid-in capital (in the absence of retained earnings) in the accompanying statement of redeemable convertible preferred stock and stockholders' equity (deficit).

Stockholders' Equity (Deficit)	12 Months Ended
Stockholders' Equity (Deficit)	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity (Deficit)	Stockholders' Equity (Deficit) Common Stock Common stockholders are entitled to dividends as and when declared by the Board of Directors, subject to the rights of holders of all classes of stock outstanding having priority rights as to dividends. There have been no dividends declared to date. The holder of each share of common stock is entitled to one vote. On January 2, 2019, the Company amended and restated its restated certificate of incorporation to, among other things, increase its authorized shares of common stock from 1,470,000,000 to 1,675,200,000 shares. On July 11, 2019, the Company amended and restated its restated certificate of incorporation to, among other things, increase its authorized shares of common stock from 1,675,200,000 to 1,970,000,000 shares. The Company filed its amended and restated certificate of incorporation on September 23, 2019, authorizing 200,000,000 shares of common stock and 10,000,000 shares of preferred stock. On September 23, 2019, the Company closed its IPO of 4,140,000 shares of its common stock at a price to the public of $14.00 per share, including the exercise in full by the underwriters of their option to purchase 540,000 additional shares of the Company's common stock. Including the exercise of the option to purchase additional shares, the aggregate net proceeds to the Company from the offering was approximately $50.4 million, net of underwriting discounts, commissions and other offering expenses, for aggregate expenses of approximately $7.5 million. In addition, an aggregate of 7,816,643 shares of common stock, excluding warrant conversions, were issued to the holders of the Company's Series A-3, Series B-3, Series C, Series D, Series E, Series F and Series H redeemable convertible preferred stockholders upon the automatic conversion of all shares of redeemable convertible preferred stock to common stock.

Stock Option Plan

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Stock Option Plan

In December 2012, the Company's Board of Directors adopted the 2013 Stock Option Plan (the Plan). Pursuant to the Plan, employees, consultants, and directors may be granted either incentive stock options or non-qualified stock options to purchase shares of the Company's common stock. In July 2019, the number of shares reserved for issuance under the Plan was increased from 669,806 to 1,663,681 shares.

In September 2019, the Company's Board of Directors adopted, and the Company's stockholders approved, the 2019 Incentive Award Plan (the 2019 Plan). Under the 2019 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company or its subsidiaries. A total of (i) 2,011,832 shares of common stock plus (ii) shares subject to awards granted under the 2013 Plan on or before the effective date of the 2019 Plan became available for issuance under the 2019 Plan and will initially be reserved for issuance under the 2019 Plan. The 2019 Plan contains an "evergreen provision" that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2029 in an amount equal to the lesser of: (i) 4% of the outstanding capital stock on each December 31st, or (ii) such lesser amount determined by the Board of Directors. As of December 31, 2019, 1,283,996 shares remained available for future awards. Under the evergreen provision, on January 1, 2020, an additional 502,440 shares became available for issuance under the 2019 Plan.

The options generally expire ten years after the date of grant and are exercisable to the extent vested. Vesting is established by the Board of Directors and is generally four years from the date of grant.

Activity under the Company's stock option plans is set forth below:


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	661,180	$	1.22	9.52	$	6,198
Granted	816,356	$	13.99
Exercised	(1,548)	$	2.41
Forfeited	(99,967)	$	7.50
Expired	(479)	$	42.08
Outstanding, December 31, 2019	1,375,542	$	8.33	9.16	$	23,654
Vested and expected to vest, December 31, 2019	1,375,542	$	8.33	9.16	$	23,654
Options exercisable, December 31, 2019	203,344	$	3.49	7.85	$	4,625

The weighted-average grant date fair value per share of employee options granted to employees during the years ended December 31, 2019 and 2018 was $7.79 and $0.17, respectively. The intrinsic value is calculated as the difference between the fair value of the Company's common stock and the exercise price of the stock options. The fair value of the Company's common stock is $25.40 and $9.92 per share at December 31, 2019 and 2018, respectively. The intrinsic value of options exercised for the years ended December 31, 2019 and 2018 was an immaterial amount and zero, respectively.

Stock-Based Compensation Expense

The fair value of employee stock options was estimated using the following assumptions to determine the fair value of stock options granted:


	Years Ended December 31,
	2019	2018
Expected volatility	46%-59%	70%
Risk-free interest rate	1.6%-2.6%	1.4% - 2.6%
Dividend yield	—	—
Expected term (in years)	5.75-6.08	6.08

Total non-cash stock-based compensation expense recorded related to options granted in the statement of operations is as follows (in thousands):


	Years Ended December 31,
	2019		2018
Cost of revenue	$	9	$	12
Selling, general and administrative	445		93
Research and development	118		9
Total	$	572	$	114

As of December 31, 2019, total unrecognized compensation cost was $5.6 million, which is expected to be recognized over a remaining weighted-average vesting period of 3.3 years.

Employee Stock Purchase Plan

In September 2019, the Board of Directors adopted the Employee Stock Purchase Plan (the ESPP). The ESPP became effective on the day the ESPP was adopted by the Company's Board of Directors. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. A total of 120,000 shares of common stock was initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be annually increased on the first day of each fiscal year during the term of the ESPP, beginning with the 2020 calendar year through January 1, 2029 in an amount equal to the lesser of (i) 1% of the outstanding capital stock on December 31st, or (ii) such lesser amount determined by the Board of Directors. Under the evergreen provision, on January 1, 2020, an additional 125,610 shares became available for issuances under the ESPP. There has been no stock-based compensation expense incurred related to the ESPP for the year ended December 31, 2019.

Common stock reserved for future issuance consists of the following at December 31, 2019:


Warrants to purchase common stock						461,273
Common stock option grants issued and outstanding						1,375,542
Common shares available for grant under the stock option plan						1,283,996
Common shares available for future issuance under ESPP						120,000
Total						3,240,811

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

Income TaxesThe provision for income taxes consists of the following (in thousands):


	Years Ended December 31,
	2019		2018
Current:
Federal	$	—	$	—
State	5		27
Total current	5		27
Deferred:
Federal	10		10
State	10		21
Total deferred	20		31
Provision for income tax	$	25	$	58

The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows:


	Years Ended December 31,
	2019		2018
Federal statutory tax rate	(21.0)	%	(21.0)	%
State income taxes, net of federal tax benefits	(3.6)	%	(3.9)	%
Change in fair value of preferred stock liabilities	(0.5)	%	0.8	%
Change in valuation allowance	(36.1)	%	23.2	%
Limitation of net operating losses	59.8	%	—	%
Other	1.6	%	1.6	%
Effective tax rate	0.2	%	0.7	%

Significant components of the Company’s deferred tax assets at December 31, 2019 and 2018 are shown below. A valuation allowance has been established as realization of the Company’s deferred tax assets has not met the more likely-than-not threshold requirement. If the Company’s judgment changes and it is determined that the Company will be able to realize these deferred tax assets, the tax benefits relating to any reversal of the valuation allowance on deferred tax assets will be accounted for as a reduction to income tax expense (in thousands).


	December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	15,287	$	18,937
Research and development tax credits	419		313
Accruals, reserves and other	590		1,394
Interest expense	744		691
Basis differences in fixed and intangible assets	225		230
Total gross deferred tax assets	17,265		21,565
Less: Valuation allowance	(16,797)		(21,138)
Deferred tax assets, net	468		427
Deferred tax liabilities:
Financing and acquisition-related liabilities	(336)		(338)
Indefinite lived assets	(396)		(334)
Deferred tax liabilities, net	(732)		(672)
Net deferred tax liabilities	$	(264)	$	(245)

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2019 and 2018, which related primarily to increases in net operating loss carryforwards, accrued revenue and accruals and reserves were as follows (in thousands):


	December 31,
	2019		2018
Valuation allowance at the beginning of the year	$	21,138	$	19,929
Decreases recorded as benefits to income tax provision	(4,341)		—
Increases recorded to income tax provision	—		1,209
Valuation allowance at the end of the year	$	16,797	$	21,138

At December 31, 2019 and 2018, the Company had federal net operating loss carryforwards of approximately $60.7 million and $80.8 million, respectively. At December 31, 2019 and 2018, the Company had state net operating loss carryforwards of $43.5 million and $30.6 million, respectively. Approximately $43.5 million of the federal tax loss carryforwards will begin to expire in 2022, unless previously utilized. The federal net operating loss carryforwards generated in after December 31, 2017 of $17.2 million will carryforward indefinitely and be available to offset up to 80% of future taxable income each year. The Company’s state tax loss carryforwards will expire in 2032, unless previously utilized.

At December 31, 2019, the Company's deferred tax assets are primarily comprised of federal and state tax net operating loss carryforwards. The Company completed a formal study through the year ended December 31, 2019 and determined ownership changes within the meaning of Internal Revenue Code (IRC), Section 382 had occurred in 2003, 2008, 2012, 2017 and 2019. Based on the analysis, $61.8 million of the Company's tax attribute carryforwards through December 31, 2017 cannot be utilized under IRC Section 382. The Company's ability to utilize net operating loss carryforwards generated after December 31, 2017 will not expire under the Tax Cuts and Jobs Act of 2017. The Company adjusted tax attribute carry forwards and deferred tax assets accordingly. As the deferred tax assets associated with the tax attribute carry forwards were fully offset by a valuation allowance, a corresponding reduction in the Company's valuation allowance was also recorded, resulting in no income tax impact.

The Company is subject to taxation in the U.S. and in various state jurisdictions. The Company’s tax years for 2002 and forward are subject to examination by the U.S. and state tax authorities due to the carryforward of unutilized net operating losses and research and development credits.

The Company recognizes interest and / or penalties related to income tax matters in its provision for income taxes. The Company does not have any accruals for, and did not recognize any, interest or penalties in these financial statements in any period presented.

Uncertain Tax Positions

At December 31, 2019 and 2018, the Company had no unrecognized tax benefits.

The Company does not believe that the balance of unrecognized tax benefits will materially change within the next twelve months.

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Parties	Related Parties The Company entered into a consulting services agreement, as amended, with a member of the Company's Board of Directors under which this board member provides certain scientific consulting services to the Company. Under this agreement, as amended in June 2018, this board member is compensated at a bi-weekly rate of $5,000 (plus reimbursement for certain administrative and travel related expenses) and received options to purchase 544 shares of common stock in November 2017, the commencement date of the agreement. Total amounts paid to this board member under this agreement for the years ended December 31, 2019 and 2018, were $130,000 and $126,000, respectively, which was recorded in research and development expenses in the accompanying statements of operations. The Company accounted for the grant of options as an award to a non-employee and measures compensation cost for this award based on the value of the award at the date the consulting services are complete. The options granted to this board member were granted at an exercise price of $0.367 (the estimated fair value of share of common stock on the grant date using an OPM model), and vests over a three-year term expected to coincide with the period the board member is expected to provide consulting services to the Company. The estimated fair value of the awards and related compensation cost recognized during the years ended December 31, 2019 and 2018 was immaterial. All compensation cost related to these awards is recorded in research and development expenses in the accompanying statements of operations. Effective July 12, 2019, this consultant no longer serves on the Company's Board of Directors. In September 2011, the Company entered into a license agreement with the Company's former Chief Scientific Officer, and a related company, De Novo Diagnostics, Inc. The license agreement, covering novel methods for monitoring low-dose methotrexate therapy, relates to technology developed by the Company's former Chief Scientific Officer prior to joining the Company. The technology has yet to be used by the Company. Under the agreement, the Company's Chief Scientific Officer will be eligible to receive up to $0.6 million upon the achievement of certain sales milestones and an ongoing royalty of 5% on sales. The third tranche closing of the Series F financing, the closings of the Series G financing and the Series H financing described in Note 8 were issued to existing holders of the Company's redeemable convertible preferred stock, including certain members of our Board of Directors.

401(k) Plan	12 Months Ended
401(k) Plan	Dec. 31, 2019
Retirement Benefits [Abstract]
401(k) Plan	Note 13. 401(k) Plan The Company sponsors an employee savings plan that qualifies as a deferred salary arrangement under Section 401(k) of the Code. Participating employees may defer up to the Internal Revenue Service annual contribution limit. Additionally, the Company may elect to make contributions into the savings plan at its sole discretion. For the years ended December 31, 2019 and 2018, the Company made contributions to the Plan at 3% of qualified employee compensation, which totaled approximately $0.4 million.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent to December 31, 2019, stock options for 290,000 shares of the Company's common stock were granted to Company employees. In March 2020, the Company entered into a new lease agreement related to expanded office and laboratory space in the building attached to the Company's existing headquarters. The initial term of the lease agreement is five years and nine months, expiring in January 2026. The lease agreement provides for monthly base rent of $12,724 beginning in May 2020, which amount shall increase 3% annually beginning in February 2022. The lease agreement does not include any right or option to extend the term after its expiration. In March 2020, the Company entered into a lease extension on our existing office space located adjacent to the Company's headquarters. The lease extension extends the term from February 2021, until its new expiration in January 2026. The lease extension provides that the base monthly rent for the leased space shall be $19,000, for the 12-month period beginning in February 2021, which amount shall increase $600 on a monthly basis each additional 12-month period until its expiration. In addition, the lease extension added an option for the Company to extend the term of the lease for one five year period, commencing when the prior term expires. In addition, in March 2020, the Company entered into a lease amendment relating to its headquarters. The lease amendment extends to the term of the lease from April 2020, until its new expiration in January 2026. The lease amendment provides that the base monthly rent for the leased space shall be $16,308.57, for the 10-month period beginning in April 2020, which amount shall increase to $17,325 in February 2021, and shall increase 3% annually thereafter. In addition, the lease amendment added an option for the Company to extend the term of the lease for one five year period, commencing when the prior term expires. In March 2020 the World Health Organization declared the outbreak of a novel coronavirus (COVID-19) as a pandemic. As a result, the Company is taking the steps to protect the health, safety and well-being of its employees, Associates, and communities by equipping various staff members to work remotely for an uncertain period of time. The Company has started to experience challenges resulting from social distancing and stay-at home orders through a reduction in testing volumes. The Company cannot reasonably estimate the length or severity of this pandemic, which may result in a material adverse impact on its balance sheets, results of operations and cash flows in 2020.

Summary Of Significant Accounting Policies - Policies	12 Months Ended
Summary Of Significant Accounting Policies - Policies	Dec. 31, 2019
Accounting Policies [Abstract]
Concentration of Credit Risk and Other Risk and Uncertainties	Concentration of Credit Risk and Other Risk and Uncertainties Financial instruments that potentially subject the Company to credit risk consist principally of cash, cash equivalents, and accounts receivable. Substantially all the Company's cash and cash equivalents are held at one financial institution that management believes is of high credit quality. Such deposits may, at times, exceed federally insured limits.
Fair Value Measurements	Fair Value Measurements The carrying value of the Company's cash and cash equivalents, other assets and accrued liabilities approximate fair value due to the short-term nature of these items. Based on the borrowing rates currently available to the Company for debt with similar terms and consideration of default and credit risk, the carrying value of the Company's long-term borrowings approximates its fair value, which is considered a Level 2 input. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities; Level 2 - Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 - Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Prior to the IPO, the Company's redeemable convertible preferred stock warrant liabilities were measured at fair value on a recurring basis and were classified as Level 3 liabilities. The Company recorded subsequent adjustments to reflect the increase or decrease in estimated fair value at each reporting date in current period earnings.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly-liquid investments purchased with a remaining maturity date upon acquisition of three months or less to be cash equivalents and are stated at cost, which approximates fair value.
Property and Equipment	Property and EquipmentProperty and equipment are stated at cost, net of depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of the estimated useful life or the remaining term of the related lease. Maintenance and repairs are charged to expense as incurred, and improvements and betterments are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in other income or expense in the statements of operations in the period realized.
Long-lived Assets	Long-lived Assets The Company’s long-lived assets are comprised principally of its property and equipment, finite lived intangible assets, and goodwill. If the Company identifies a change in the circumstances related to its long-lived assets, such as property and equipment and intangible assets (other than goodwill), that indicates the carrying value of any such asset may not be recoverable, the Company will perform an impairment analysis. A long-lived asset (other than goodwill) is deemed to be impaired when the undiscounted cash flows expected to be generated by the asset (or asset group) are less than the asset’s carrying amount. Any required impairment loss would be measured as the amount by which the asset’s carrying value exceeds its fair value, and would be recorded as a reduction in the carrying value of the related asset and a charge to operating expense. Goodwill is reviewed for impairment annually (during the fourth quarter) or more frequently if indicators of impairment exist. As the Company operates in a single operating segment and reporting unit, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a quantitative assessment. If, after assessing qualitative factors, the Company determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing a quantitative assessment is unnecessary. If deemed necessary, a quantitative assessment compares the fair value of the reporting unit with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired; otherwise, an impairment loss is recorded. There was no indication of impairment of goodwill for any periods presented.
Clinical Studies	Clinical StudiesFrom time to time, the Company engages in efforts to scientifically measure and document the application and efficacy of its various testing products. These arrangements typically require the Company to pay a fee to a third-party scientific investigator (usually a physician or research institution) for each subject enrolled in a clinical study, and the Company accrues expenses associated with these efforts as subjects are enrolled in each study. Expenses associated with clinical study activities are recorded in research and development expenses in the accompanying statement of operations.
Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock Prior to the completion of the IPO, the Company had multiple classes of redeemable convertible preferred stock, all of which were classified as temporary equity in the accompanying balance sheet as the redemption of the shares were outside of the Company's control. Redeemable convertible preferred stock which was redeemable on or after a certain date at the option of the holder was accreted to its redemption value from the date of issuance to the earliest redemption date. In connection with the completion of the IPO in September 2019, all outstanding shares of redeemable convertible preferred stock were automatically converted into an aggregate of 7,816,643 shares of common stock, excluding warrant conversions. Redeemable Convertible Preferred Stock Warrants Prior to the completion of the IPO, the Company accounted for its redeemable convertible preferred stock warrants as liabilities based upon the characteristics and provisions of each instrument. The redeemable convertible preferred stock warrants were recorded at their fair value on the date of issuance and were revalued on each subsequent balance sheet date, with fair value changes recognized as increases or reductions in the statements of operations. Upon the completion of the IPO, all remaining outstanding warrants to purchase shares of redeemable convertible preferred stock were automatically converted into warrants to purchase shares of common stock. As such, the warrants no longer require liability accounting and the then fair value of the warrant liability was reclassified into stockholders’ equity. The Company performed the final remeasurement of the warrant liabilities as of the IPO closing date. See Note 7 for the amounts associated with the fair value measurements and Note 5 for further discussion on the remaining warrants.
Revenue Recognition	Revenue Recognition Substantially all of the Company's revenue has been derived from sales of its testing products and is primarily comprised of a high volume of relatively low-dollar transactions. The Company primarily markets its testing products to rheumatologists and their physician assistants in the United States. The healthcare professionals who order the Company's testing products and to whom test results are reported are generally not responsible for payment for these products. The parties that pay for these services (the Payers) consist of healthcare insurers, government payers (primarily Medicare and Medicaid), client payers (i.e., hospitals, other laboratories, etc.), and patient self-pay. The Company's service is a single performance obligation that is completed upon the delivery of test results to the prescribing physician which triggers revenue recognition. Payers are billed at the Company's list price. Net revenues recognized consist of amounts billed net of allowances for differences between amounts billed and the estimated consideration the Company expects to receive from such payers. The process for estimating revenues and the ultimate collection of accounts receivable involves significant judgment and estimation. The Company follows a standard process, which considers historical denial and collection experience, insurance reimbursement policies and other factors, to estimate allowances and implicit price concessions, recording adjustments in the current period as changes in estimates. Further adjustments to the allowances, based on actual receipts, is recorded upon settlement. The transaction price is estimated using an expected value method on a portfolio basis. The Company's portfolios are grouped per payer (i.e. each individual third-party insurance, Medicare, client payers, patient self-pay, etc.) and per test basis. Collection of the Company's net revenues from payers is normally a function of providing complete and correct billing information to the healthcare insurers and generally occurs within 30 to 90 days of billing. Contracts do not contain significant financing components based on the typical period of time between performance of services and collection of consideration. The Company early adopted Accounting Standards Codification (ASC) Topic 606, Revenue from Contracts with Customers (Topic 606) as of January 1, 2018 using a cumulative-effect adjustment to the opening balance of accumulated deficit and accounts receivable of $3.1 million.
Research and Development	Research and Development Costs associated with research and development activities are expensed as incurred and include, but are not limited to, personnel-related expenses, including stock-based compensation expense, materials, laboratory supplies, consulting costs, costs associated with setting up and conducting clinical studies and allocated overhead including rent and utilities.
Advertising and Marketing Cost	Advertising and Marketing Costs Costs associated with advertising and marketing activities are expensed as incurred. Total advertising and marketing costs were approximately $1.6 million and $1.4 million for the years ended December 31, 2019 and 2018, respectively, and are included in selling, general and administrative expenses in the accompanying statements of operations.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes compensation expense for all stock-based awards to employees and directors based on the grant-date estimated fair values over the requisite service period of the awards (usually the vesting period) on a straight-line basis. The fair value of stock options is determined using the Black-Scholes-Merton (BSM) option pricing model, which requires management to make certain assumptions regarding a number of complex and subjective variables. Equity award forfeitures are recorded as they occur. The BSM option pricing model incorporates various estimates, including the fair value of the Company's common stock, expected volatility, expected term and risk-free interest rates. The weighted-average expected term of options was calculated using the simplified method. This decision was based on the lack of relevant historical data due to the Company's limited historical experience. In addition, due to the Company's limited historical data, the estimated volatility incorporates the historical volatility over the expected term of the award of comparable companies whose share prices are publicly available. The risk-free interest rate for periods within the contractual term of the option is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield was zero, as the Company has never declared or paid dividends and has no plans to do so in the foreseeable future.Upon the effective date of the IPO, the Company began using the closing price of its common stock as the fair value of its common stock on the corresponding date. Prior to the completion of the IPO in September 2019, due to the absence of a public market for the Company's common stock, it was necessary to estimate the fair value of the common stock underlying the Company's stock-based awards when performing fair value calculations using the BSM option pricing model. The fair value of the common stock underlying the Company's stock-based awards was assessed on each grant date by the Company's board of directors (Board of Directors).
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from nonowner sources. There have been no items qualifying as other comprehensive loss and, therefore, for all periods presented, the Company's comprehensive loss was the same as its reported net loss.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would adjust the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.
Net Loss Per Share	Net Loss Per Share Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Potentially dilutive common stock equivalents are comprised of redeemable convertible preferred stock, warrants for the purchase of redeemable convertible preferred and common stock and options outstanding under the Company's stock option plans. For the years ended December 31, 2019 and 2018, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as the inclusion of the potentially dilutive securities would be antidilutive.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations as, and manages its business in, one operating segment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB), or other standard setting bodies and adopted by the Company as of the specified effective date. Under the Jumpstart Our Business Startups Act of 2012 (JOBS Act), the Company meets the definition of an emerging growth company. The Company has elected to use the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption. In February 2016, the FASB issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842). The new topic supersedes Topic 840, Leases, and increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and requires disclosures of key information about leasing arrangements. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, which provides narrow amendments to clarify how to apply certain aspects of the new lease standard, and ASU 2018-11, Leases: Targeted Improvements, which was issued to provide relief to companies from restating comparative periods. Pursuant to this ASU, in the period of adoption the Company will not restate comparative periods presented in its financial statements. The effective date of this guidance for public companies is for reporting periods beginning after December 15, 2018. As an emerging growth company as defined in the JOBS Act, the Company has elected to delay adoption of this ASU until January 1, 2021. Topic 842 mandates a modified retrospective transition method. The Company intends to adopt the new lease standard using a cumulative effect to accumulated deficit and will elect the package of practical expedients, which among other things will allow the Company to carry forward its historical lease classification. The Company is currently evaluating the impact of Topic 842 on its financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. This update is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2018-13 on its financial statements.

Summary Of Significant Accounting Policies - (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Concentration of Risk, by Risk Factor and Significant Payer

For each significant payer, revenue as a percentage of total revenue and accounts receivable as a percentage of total accounts receivable are as follows:


	Revenue
		Years Ended December 31,
		2019		2018
Medicare		25	%	30	%
Blue Shield		12	%	14	%
United Healthcare		11	%	12	%
Medicare Advantage		11	%	10	%
Janssen (SIMPONI^®)		*		*



*						Less than 10%.


	Accounts Receivable
	December 31,
	2019		2018
Medicare	*		26	%
Blue Shield	15	%	16	%
United Healthcare	22	%	11	%
Medicare Advantage	*		11	%
Janssen (SIMPONI^®)	19	%	*



*						Less than 10%.

Disaggregation of Revenue

The following table includes the Company's revenues as disaggregated by payer category (in thousands):


	Years Ended December 31,
	2019		2018
Revenue:
Healthcare insurers	$	23,984	$	21,070
Government	9,896		10,024
Client	4,392		608
Other(1)	639		738
Janssen (SIMPONI^®)	1,476		—
Total revenue	$	40,387	$	32,440

(1)Includes patient self-pay that is immaterial.

Schedule of Restricted Cash and Cash Equivalents

Cash, cash equivalents and restricted cash presented in the accompanying statements of cash flows consist of the following (in thousands):


	December 31,
	2019		2018
Cash and cash equivalents	$	72,084	$	13,164
Restricted cash	100		100
	$	72,184	$	13,264

Schedule of Cash and Cash Equivalents

Cash, cash equivalents and restricted cash presented in the accompanying statements of cash flows consist of the following (in thousands):


	December 31,
	2019		2018
Cash and cash equivalents	$	72,084	$	13,164
Restricted cash	100		100
	$	72,184	$	13,264

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares):


	Years Ended December 31,
	2019	2018
Redeemable convertible preferred stock	—	5,202,940
Warrants to purchase redeemable convertible preferred stock	—	224,493
Warrants to purchase common stock	461,273	934,789
Common stock options	1,375,542	661,180
Total	1,836,815	7,023,402

Other Financial Information - (Tables)

12 Months Ended

Dec. 31, 2019

Other Financial Information [Abstract]

Prepaid expenses table

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2019		2018
Diagnostic testing supplies	$	1,427	$	1,174
Prepaid product royalties	123		176
Prepaid maintenance and insurance contracts	1,768		698
Other prepaid assets	133		148
Prepaid and other current assets	$	3,451	$	2,196

Property and equipment

Property and equipment consist of the following (in thousands):


	December 31,
	2019		2018
Furniture and fixtures	$	25	$	25
Laboratory equipment	2,228		1,855
Computer equipment and software	851		796
Leasehold improvements	424		399
Construction in progress	247		310
Total property and equipment	3,775		3,385
Less: accumulated depreciation and amortization	(2,395)		(1,819)
Property and equipment, net	$	1,380	$	1,566

Accrued liabilities

Accrued liabilities consist of the following (in thousands):


	December 31,
	2019		2018
Accrued payroll and related expenses	$	2,362	$	2,111
Accrued deferred offering costs	—		355
Accrued interest	145		178
Accrued purchases of goods and services	319		243
Accrued royalties	727		602
Accrued clinical study activity	40		146
Capital lease obligations, current portion	238		81
Other accrued liabilities	588		207
Accrued liabilities	$	4,419	$	3,923

Borrowings - (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of Future Minimum Aggregate Payments for Outstanding Borrowings

As of December 31, 2019, future minimum aggregate payments, including interest, for outstanding borrowings under the Loan Amendment are as follows (in thousands):


	Years Ending December 31,

2020	$	1,725
2021	1,755
2022	2,996
2023	15,619
2024	14,280
Total	36,375
Less:
Unamortized debt discount and issuance costs	(390)
Interest	(10,131)
Total borrowings, net of discounts and debt issuance costs	$	25,854

Warrants to Purchase Common or Preferred Stock - (Tables)

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Schedule of Outstanding Warrants

The following warrants to purchase common stock were outstanding as of December 31, 2019:

Exercise Price

Issuance date

Expiration date

Common stock warrants

282,402

1.84

January 19, 2016

January 19, 2026

Common stock warrants

74,018

1.84

March 31, 2016

March 31, 2026

Common stock warrants

131

1.84

April 1, 2016

April 1, 2026

Common stock warrants (1)

83,778

14.32

September 8, 2017

September 8, 2024

Common stock warrants (1)

20,944

14.32

December 7, 2018

December 7, 2025

461,273

(1) Prior to the conversion upon IPO, the remaining warrants were for the purchase of Series F redeemable convertible preferred stock.

Commitment and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Future minimum payments

Minimum annual lease payments under non-cancelable lease arrangements at December 31, 2019 are as follows (in thousands):


Years Ending December 31,	Capital Leases		Operating Leases
2020	$	272	$	411
2021	272		34
2022	246		—
2023	159		—
2024	—		—
Total minimum lease payments	949		$	445
Less: amount representing interest	(75)
Present value of future minimum lease payments	874
Less: current portion	(238)
Long-term capital lease obligations	$	636

Schedule of Future Minimum Rental Payments for Operating Leases

Minimum annual lease payments under non-cancelable lease arrangements at December 31, 2019 are as follows (in thousands):


Years Ending December 31,	Capital Leases		Operating Leases
2020	$	272	$	411
2021	272		34
2022	246		—
2023	159		—
2024	—		—
Total minimum lease payments	949		$	445
Less: amount representing interest	(75)
Present value of future minimum lease payments	874
Less: current portion	(238)
Long-term capital lease obligations	$	636

Fair Value Measures and Disclosures (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Financial Instrument Measured on a Recurring Basis

The following table sets forth the Company's financial instruments that were measured at fair value on a recurring basis within the fair value hierarchy (in thousands):


	December 31, 2019
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	70,760	$	70,760	$	—	$	—


	December 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	8,618	$	8,618	$	—	$	—
Liabilities:
Redeemable convertible preferred stock warrant liabilities	$	1,503	$	—	$	—	$	1,503

Schedule of Fair Value, Financial Instruments Measured on Recurring Basis, Level 3 Hierarchy

The following table includes a roll-forward of the financial instruments measured on a recurring basis and classified within Level 3 of the fair value hierarchy (in thousands):


	Liability Classified Warrants
Balances at December 31, 2017	$	896
Issuance of warrants to purchase shares of Series F redeemable convertible preferred stock in connection with 2017 Term Loan (Note 4)	289
Remeasurement of financial instruments	318
Balances at December 31, 2018	1,503
Remeasurement of financial instruments	(267)
Net exercise of preferred stock warrants	(510)
Reclassification of liability classified warrants to stockholders' equity (deficit)	(726)
Balance at December 31, 2019	$	—

Stock Option Plan (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

Activity under the Company's stock option plans is set forth below:


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	661,180	$	1.22	9.52	$	6,198
Granted	816,356	$	13.99
Exercised	(1,548)	$	2.41
Forfeited	(99,967)	$	7.50
Expired	(479)	$	42.08
Outstanding, December 31, 2019	1,375,542	$	8.33	9.16	$	23,654
Vested and expected to vest, December 31, 2019	1,375,542	$	8.33	9.16	$	23,654
Options exercisable, December 31, 2019	203,344	$	3.49	7.85	$	4,625

Schedule of Fair Value Assumptions, Stock Options

The fair value of employee stock options was estimated using the following assumptions to determine the fair value of stock options granted:


	Years Ended December 31,
	2019	2018
Expected volatility	46%-59%	70%
Risk-free interest rate	1.6%-2.6%	1.4% - 2.6%
Dividend yield	—	—
Expected term (in years)	5.75-6.08	6.08

Schedule of Non-cash Stock-based Compensation Expense

Total non-cash stock-based compensation expense recorded related to options granted in the statement of operations is as follows (in thousands):


	Years Ended December 31,
	2019		2018
Cost of revenue	$	9	$	12
Selling, general and administrative	445		93
Research and development	118		9
Total	$	572	$	114

Schedule of Common Stock Reserved For Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2019:


Warrants to purchase common stock						461,273
Common stock option grants issued and outstanding						1,375,542
Common shares available for grant under the stock option plan						1,283,996
Common shares available for future issuance under ESPP						120,000
Total						3,240,811

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

The provision for income taxes consists of the following (in thousands):


	Years Ended December 31,
	2019		2018
Current:
Federal	$	—	$	—
State	5		27
Total current	5		27
Deferred:
Federal	10		10
State	10		21
Total deferred	20		31
Provision for income tax	$	25	$	58

Schedule of Effective Income Tax Rate Reconciliation

The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows:


	Years Ended December 31,
	2019		2018
Federal statutory tax rate	(21.0)	%	(21.0)	%
State income taxes, net of federal tax benefits	(3.6)	%	(3.9)	%
Change in fair value of preferred stock liabilities	(0.5)	%	0.8	%
Change in valuation allowance	(36.1)	%	23.2	%
Limitation of net operating losses	59.8	%	—	%
Other	1.6	%	1.6	%
Effective tax rate	0.2	%	0.7	%

Schedule of Deferred Tax Assets and Liabilities

If the Company’s judgment changes and it is determined that the Company will be able to realize these deferred tax assets, the tax benefits relating to any reversal of the valuation allowance on deferred tax assets will be accounted for as a reduction to income tax expense (in thousands).


	December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	15,287	$	18,937
Research and development tax credits	419		313
Accruals, reserves and other	590		1,394
Interest expense	744		691
Basis differences in fixed and intangible assets	225		230
Total gross deferred tax assets	17,265		21,565
Less: Valuation allowance	(16,797)		(21,138)
Deferred tax assets, net	468		427
Deferred tax liabilities:
Financing and acquisition-related liabilities	(336)		(338)
Indefinite lived assets	(396)		(334)
Deferred tax liabilities, net	(732)		(672)
Net deferred tax liabilities	$	(264)	$	(245)

Summary of Valuation Allowance


	December 31,
	2019		2018
Valuation allowance at the beginning of the year	$	21,138	$	19,929
Decreases recorded as benefits to income tax provision	(4,341)		—
Increases recorded to income tax provision	—		1,209
Valuation allowance at the end of the year	$	16,797	$	21,138

Organization - (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Sep. 23, 2019 USD ($) $ / shares shares	Sep. 06, 2019	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Subsidiary, Sale of Stock [Line Items]
Reverse stock split ratio, common stock		0.0054
Cash and cash equivalents \| $			$ 72,084	$ 13,164
Accumulated deficit \| $			$ 164,602	$ 152,564
Common Stock
Subsidiary, Sale of Stock [Line Items]
Stock issued upon conversion of redeemable convertible preferred shares (in shares)			7,816,643
Common Stock \| IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in public offering	4,140,000
Shares issued in public offering, price per share (in dollars per share) \| $ / shares	$ 14.00
Proceeds from public offering, net \| $	$ 50,400
Stock issued upon conversion of redeemable convertible preferred shares (in shares)	7,816,643
Common Stock \| Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in public offering	540,000

Summary Of Significant Accounting Policies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2016
New Accounting Pronouncement, Early Adoption [Line Items]
Restricted cash	$ 100,000	$ 100,000
Cumulative effect of changes in accounting principle related to revenue recognition			$ 3,086,000
Revenue	40,387,000	32,440,000
Advertising Expense	1,600,000	1,400,000
Minimum
New Accounting Pronouncement, Early Adoption [Line Items]
Joint venture, quarterly promotion fee	750
Maximum
New Accounting Pronouncement, Early Adoption [Line Items]
Joint venture, quarterly promotion fee	1,250
Shipping and Handling
New Accounting Pronouncement, Early Adoption [Line Items]
Cost of revenue	1,400,000	1,200,000
ASU 606
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect of changes in accounting principle related to revenue recognition			$ 3,100,000
Janssen (SIMPONI)
New Accounting Pronouncement, Early Adoption [Line Items]
Revenue	$ 1,476,000	$ 0
Other assets
New Accounting Pronouncement, Early Adoption [Line Items]
Restricted cash				$ 100,000

Summary Of Significant Accounting Policies - Revenue by Major Payers (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Revenue Benchmark \| Supplier Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		97.00%	95.00%
Medicare \| Revenue Benchmark \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		25.00%	30.00%
Medicare \| Accounts Receivable \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue	26.00%
Blue Shield \| Revenue Benchmark \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		12.00%	14.00%
Blue Shield \| Accounts Receivable \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue	16.00%	15.00%
United Healthcare \| Revenue Benchmark \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		11.00%	12.00%
United Healthcare \| Accounts Receivable \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue	11.00%	22.00%
Medicare Advantage \| Revenue Benchmark \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		11.00%	10.00%
Medicare Advantage \| Accounts Receivable \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue	11.00%
Janssen (SIMPONI) \| Accounts Receivable \| Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		19.00%
AVISE CTD Test \| Revenue Benchmark \| Product Concentration Risk
Disaggregation of Revenue [Line Items]
Percent of total revenue		82.00%	82.00%

Summary Of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 40,387	$ 32,440
Healthcare insurers
Disaggregation of Revenue [Line Items]
Revenue	23,984	21,070
Government
Disaggregation of Revenue [Line Items]
Revenue	9,896	10,024
Client
Disaggregation of Revenue [Line Items]
Revenue	4,392	608
Other
Disaggregation of Revenue [Line Items]
Revenue	639	738
Janssen (SIMPONI)
Disaggregation of Revenue [Line Items]
Revenue	$ 1,476	$ 0

Summary Of Significant Accounting Policies - Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 72,084	$ 13,164
Restricted cash	100	100
Total cash, cash equivalents and restricted cash	$ 72,184	$ 13,264	$ 11,341

Summary Of Significant Accounting Policies - Securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Anti-dilutive securities excluded from computation	1,836,815	7,023,402
Redeemable convertible preferred stock
Class of Stock [Line Items]
Anti-dilutive securities excluded from computation	0	5,202,940
Warrants to purchase redeemable convertible preferred stock
Class of Stock [Line Items]
Anti-dilutive securities excluded from computation	0	224,493
Warrants to purchase common stock
Class of Stock [Line Items]
Anti-dilutive securities excluded from computation	461,273	934,789
Common stock options
Class of Stock [Line Items]
Anti-dilutive securities excluded from computation	1,375,542	661,180

Other Financial Information - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 600	$ 600
Property and equipment, gross	3,775	3,385
Assets under capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 800	$ 400

Other Financial Information - Prepaid expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Diagnostic testing supplies	$ 1,427	$ 1,174
Prepaid product royalties	123	176
Prepaid maintenance and insurance contracts	1,768	698
Other prepaid assets	133	148
Prepaid and other current assets	$ 3,451	$ 2,196

Other Financial Information - Property and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,775	$ 3,385
Less: accumulated depreciation and amortization	(2,395)	(1,819)
Property and equipment, net	1,380	1,566
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	25	25
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	2,228	1,855
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	851	796
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	424	399
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 247	$ 310

Other Financial Information - Accrued liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Accrued payroll and related expenses	$ 2,362	$ 2,111
Accrued deferred offering costs	0	355
Accrued interest	145	178
Accrued purchases of goods and services	319	243
Accrued royalties	727	602
Accrued clinical study activity	40	146
Capital lease obligations, current portion	238	81
Other accrued liabilities	588	207
Accrued liabilities	$ 4,419	$ 3,923

Borrowings - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 07, 2018	Sep. 30, 2017	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2019	Sep. 30, 2019	Dec. 31, 2017
Debt Instrument [Line Items]
Term loan borrowings				$ 0	$ 4,995
Warrants issued to purchase redeemable convertible preferred stock				461,273
Number of common shares to be called upon exercise of warrants							512,363
Series F redeemable convertible preferred stock
Debt Instrument [Line Items]
Number of common shares to be called upon exercise of warrants							104,722
Loan payable \| Capital Royalty Partners II LP
Debt Instrument [Line Items]
Loan repayment			$ 17,800
2017 Term loan \| Loan payable
Debt Instrument [Line Items]
Term loan, issuance costs								$ 100
2017 Term loan \| Loan payable \| Innovatus Life Sciences Lending Fund
Debt Instrument [Line Items]
Term loan borrowings	$ 5,000	$ 20,000
Term loan, interest rate						8.50%
Term loan, paid in-kind, interest rate						2.00%
Term loan, effective interest rate				10.00%
Term loan, fee incurred upon payment of final installment				$ 1,000
Term loan, prepayment premium percentage				3.00%
Term loan, annual reduction in prepayment penalty percentage				100.00%
Term loan covenant, minimum unrestricted cash balance				$ 2,000
Term loan covenant, increase to interest rate				4.00%
Term loan, issuance costs								$ 400
2017 Term loan \| Loan payable \| Innovatus Life Sciences Lending Fund \| Series F redeemable convertible preferred stock
Debt Instrument [Line Items]
Warrants issued to purchase redeemable convertible preferred stock	3,846,154							15,384,615
Warrants issued to purchase redeemable convertible preferred stock, exercise price (in dollars per share)								$ 0.078
Number of common shares to be called upon exercise of warrants								104,722
2017 Term loan \| Paid in-kind note \| Innovatus Life Sciences Lending Fund
Debt Instrument [Line Items]
Term loan, paid in-kind loans issued				$ 500

Borrowings - Future minimum payments (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Debt Disclosure [Abstract]
2020	$ 1,725
2021	1,755
2022	2,996
2023	15,619
2024	14,280
Total	36,375
Unamortized debt discount and issuance costs	(390)
Interest	(10,131)
Total borrowings, net of discounts and debt issuance costs	$ 25,854

Warrants to Purchase Common or Preferred Stock - Narrative (Details)	1 Months Ended
	Sep. 30, 2019 shares
Temporary Equity [Line Items]
Number of common shares called upon exercise of warrants	512,363
Number of warrants exercised	569,184
Number of warrants unexercised and terminated	9,054
Series F redeemable convertible preferred stock
Temporary Equity [Line Items]
Number of common shares called upon exercise of warrants	104,722
Series D and Series E redeemable convertible preferred stock
Temporary Equity [Line Items]
Number of common shares called upon exercise of warrants	119,771
Net exercise of common stock warrants (in shares)	27,431

Warrants to Purchase Common or Preferred Stock - Outstanding warrants (Details)	Dec. 31, 2019 $ / shares shares
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	461,273
Warrant expiration January 19, 2026
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	282,402
Exercise Price \| $ / shares	$ 1.84
Warrant expiration March 31, 2026
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	74,018
Exercise Price \| $ / shares	$ 1.84
Warrant expiration April 1, 2026
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	131
Exercise Price \| $ / shares	$ 1.84
Warrant expiration September 8, 2024
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	83,778
Exercise Price \| $ / shares	$ 14.32
Warrant expiration December 7, 2025
Class of Warrant or Right [Line Items]
Common stock warrants (in shares)	20,944
Exercise Price \| $ / shares	$ 14.32

Commitment and Contingencies - Narrative (Details)	12 Months Ended
Commitment and Contingencies - Narrative (Details)	Dec. 31, 2019 USD ($) leaseExtention	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Rent expense	$ 500,000	$ 400,000
Minimum annual purchase commitment	$ 3,250,000
Purchase commitment, term	3 years
Minimum \| Licensing Agreements
Loss Contingencies [Line Items]
Royalty obligation, percent of net sales	3.00%
Maximum
Loss Contingencies [Line Items]
Royalty obligation, percent of net sales	20.00%
Prometheus Laboratories
Loss Contingencies [Line Items]
Remaining milestone obligation	$ 2,000,000.0
Remaining milestone obligation, fair value	0	$ 0
Advance royalties payment	$ 100,000
Prometheus Laboratories \| Minimum
Loss Contingencies [Line Items]
Royalty obligation, percent of net sales	2.50%
Prometheus Laboratories \| Maximum
Loss Contingencies [Line Items]
Royalty obligation, percent of net sales	7.50%
Future minimum royalty commitment	$ 4,200,000
Office and Laboratory
Loss Contingencies [Line Items]
Number of operating lease extensions \| leaseExtention	2
Operating lease, renewal term	36 months
Office
Loss Contingencies [Line Items]
Operating lease, renewal term	24 months

Commitment and Contingencies - Minimum annual lease payments under non-cancelable lease arrangements (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Capital Leases
2020	$ 272
2021	272
2022	246
2023	159
2024	0
Total minimum lease payments	949
Less: amount representing interest	(75)
Present value of future minimum lease payments	874
Less: current portion	(238)
Long-term capital lease obligations	636
Operating Leases
2020	411
2021	34
2022	0
2023	0
2024	0
Total minimum lease payments	$ 445

Fair Value Measurements - Fair value measurement (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Warrants
Liabilities:
Redeemable convertible preferred stock warrant liabilities		$ 1,503
Level 1 \| Warrants
Liabilities:
Redeemable convertible preferred stock warrant liabilities		0
Level 2 \| Warrants
Liabilities:
Redeemable convertible preferred stock warrant liabilities		0
Level 3 \| Warrants
Liabilities:
Redeemable convertible preferred stock warrant liabilities		1,503
Money market funds
Assets:
Money market funds	$ 70,760	8,618
Money market funds \| Level 1
Assets:
Money market funds	70,760	8,618
Money market funds \| Level 2
Assets:
Money market funds	0	0
Money market funds \| Level 3
Assets:
Money market funds	$ 0	$ 0

Fair Value Measurements- Fair value level 3 (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 1,503	$ 896
Issuance of warrants to purchase shares of Series F redeemable convertible preferred stock in connection with 2017 Term Loan (Note 4)		289
Remeasurement of financial instruments	(267)	318
Net exercise of preferred stock warrants	(510)
Reclassification of liability classified warrants to stockholders' equity (deficit)	(726)
Ending balance	$ 0	$ 1,503

Redeemable Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended						3 Months Ended			12 Months Ended		15 Months Ended
	Sep. 23, 2019	Jan. 31, 2018	Jul. 31, 2019	May 31, 2019	Mar. 31, 2019	Jan. 31, 2019	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019	Jul. 11, 2019	Jul. 10, 2019	Jan. 02, 2019	Jan. 01, 2019
Temporary Equity [Line Items]
Shares authorized (in shares)															1,038,667,059	955,500,000	955,500,000	750,300,000
Temporary Equity, Shares Redeemed upon Conversion												1,012,573,679
Deemed Dividend									$ 6,900			$ 6,860
Beneficial conversion feature, temporary equity												$ 6,741
Common Stock
Temporary Equity [Line Items]
Stock issued upon conversion of redeemable convertible preferred shares (in shares)												7,816,643
Common Stock \| IPO
Temporary Equity [Line Items]
Stock issued upon conversion of redeemable convertible preferred shares (in shares)	7,816,643
Series G redeemable convertible preferred stock
Temporary Equity [Line Items]
Shares authorized (in shares)																	205,200,000
Number of shares sold, temporary equity				51,282,048	9,615,384	88,030,905
Sale of temporary equity, price per share (in dollars per share)						$ 0.078						$ 0.078
Proceeds from sale of temporary equity				$ 4,000						$ 3,750				$ 7,600
Right to require mandatory purchase, temporary equity (in shares)				32,051,280
Consideration to be received under mandatory purchase, temporary equity				$ 2,500
Temporary Equity, Shares Redeemed upon Conversion			148,928,337
Series F redeemable convertible preferred stock
Temporary Equity [Line Items]
Number of shares sold, temporary equity		34,914,327						54,246,756
Sale of temporary equity, price per share (in dollars per share)							$ 0.078	$ 0.078					$ 0.078
Proceeds from sale of temporary equity		$ 2,700						$ 4,200
Deemed Dividend											$ 1,200
Series H redeemable convertible preferred stock
Temporary Equity [Line Items]
Shares authorized (in shares)															479,967,595
Number of shares sold, temporary equity			233,446,519
Sale of temporary equity, price per share (in dollars per share)			$ 0.04712									$ 0.047
Proceeds from sale of temporary equity			$ 11,000
Shares issued upon conversion, temporary equity (in shares)			246,521,076
Beneficial conversion feature, temporary equity									$ 6,700			$ 6,741	$ 0

Stockholders' Equity (Deficit) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 23, 2019	Dec. 31, 2019	Jul. 11, 2019	Jul. 10, 2019	Jan. 31, 2019	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Shares authorized (in shares)	200,000,000	200,000,000	1,970,000,000	1,675,200,000	1,675,200,000	1,470,000,000
Shares authorized (in shares)	10,000,000	10,000,000				0
Common Stock
Subsidiary, Sale of Stock [Line Items]
Stock issued upon conversion of redeemable convertible preferred shares (in shares)		7,816,643
IPO \| Common Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in public offering	4,140,000
Shares issued in public offering, price per share (in dollars per share)	$ 14.00
Proceeds from public offering, net	$ 50,400
Stock issuance costs	$ 7,500
Stock issued upon conversion of redeemable convertible preferred shares (in shares)	7,816,643
Over-Allotment Option \| Common Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in public offering	540,000

Stock Option Plan - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Stock Option Plan - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020	Jul. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee options, weighted-average grant date fair value per share (in dollars per share)		$ 7.79	$ 0.17
Common stock, fair value per share (in dollars per share)	$ 25.40	$ 25.40	$ 9.92
Stock options, unrecognized compensation cost	$ 5,600,000	$ 5,600,000
Stock options, cost not yet recognized, remaining weighted average vesting period		3 years 3 months 18 days
Stock-based compensation expense		$ 572,000	$ 114,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, expiration period		10 years
Stock options, vesting period		4 years
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance under Stock Option Plan	120,000	120,000
Annual percentage increase in shares available for issuance under the Plan	100.00%	100.00%
Maximum Employee payroll deduction percentage	2000.00%	2000.00%
Stock-based compensation expense	$ 0	$ 0
Employee Stock Purchase Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase (decrease) in number of shares authorized (in shares)				125,610
2013 Stock Option Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance under Stock Option Plan	669,806	669,806			1,663,681
2019 Incentive Award Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance under Stock Option Plan	2,011,832	2,011,832
Annual percentage increase in shares available for issuance under the Plan	4.00%	4.00%
Shares that remain available for future awards	1,283,996	1,283,996
2019 Incentive Award Plan \| Stock options \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase (decrease) in number of shares authorized (in shares)				502,440

Stock Option Plan - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, December 31, 2018 (in shares)	661,180
Granted (in Shares)	816,356
Exercised (in Shares)	(1,548)
Forfeited (in Shares)	(99,967)
Expired (in Shares)	(479)
Outstanding, December 31, 2019 (in shares)	1,375,542	661,180
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding, December 31, 2018, Weighted Average Exercise Price (in dollars per share)	$ 1.22
Granted, Weighted Average Exercise Price (in dollars per share)	13.99
Exercised, Weighted Average Exercise Price (in dollars per share)	2.41
Forfeited, Weighted Average Exercise Price (in dollars per share)	7.50
Expired, Weighted Average Exercise Price (in dollars per share)	42.08
Outstanding, December 31, 2019, Weighted Average Exercise Price (in dollars per share)	$ 8.33	$ 1.22
Stock Options, Additional Disclosures [Abstract]
Outstanding, Weighted Average Remaining Contractual Term	9 years 1 month 28 days	9 years 6 months 7 days
Vested and expected to vest, Weighted Average Remaining Contractual Term	9 years 1 month 28 days
Options exercisable, Weighted Average Remaining Contractual Term	7 years 10 months 6 days
Outstanding, Aggregate Intrinsic Value	$ 23,654	$ 6,198
Vested and expected to vest, Aggregate Intrinsic Value	23,654
Options exercisable, Aggregate Intrinsic Value	$ 4,625
Vested and expected to vest, December 31, 2019 (in shares)	1,375,542
Vested and expected to vest, December 31, 2019, Weighted Average Exercise Price (in dollars per share)	$ 8.33
Options exercisable, December 31, 2019 (in Shares)	203,344
Options exercised, December 31, 2019, Weighted Average Exercise Price (in dollars per share)	$ 3.49

Stock Option Plan - Fair Value Assumptions (Details)	12 Months Ended
Stock Option Plan - Fair Value Assumptions (Details)	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility rate, minimum	46.00%
Expected volatility rate, maximum	59.00%
Expected volatility		70.00%
Risk-free interest rate, minimum	1.60%	1.40%
Risk-free interest rate, maximum	2.60%	2.60%
Dividend yield	0.00%	0.00%
Expected term (in years)		6 years 29 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 9 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 29 days

Stock Option Plan - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 572	$ 114
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	9	12
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	445	93
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 118	$ 9

Stock Option Plan - Common Stock Reserved For Future Issuance (Details)	Dec. 31, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	3,240,811
Warrants to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	461,273
Common stock option grants issued and outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	1,375,542
Common shares available for grant under the stock option plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	1,283,996
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	120,000

Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal net operating loss carryforwards	$ 60.7	$ 80.8
State net operating loss carryforwards	43.5	30.6
Federal tax loss carryforwards, subject to expiration	43.5
federal net operating loss carryforwards, carryforward indefinitely	17.2
Unrecognized tax benefits	0.0	$ 0.0
Tax attribute carryforwards cannot be utilized under IRC Section 382	$ 61.8

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 0	$ 0
State	5	27
Total current	5	27
Deferred:
Federal	10	10
State	10	21
Total deferred	20	31
Provision for income tax	$ 25	$ 58

Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory tax rate	(21.00%)	(21.00%)
State income taxes, net of federal tax benefits	(3.60%)	(3.90%)
Change in fair value of preferred stock liabilities	(0.50%)	0.80%
Change in valuation allowance	(36.10%)	23.20%
Limitation of net operating losses	59.80%	0.00%
Other	1.60%	1.60%
Effective tax rate	0.20%	0.70%

Income Taxes - Reconciliation of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 15,287	$ 18,937
Research and development tax credits	419	313
Accruals, reserves and other	590	1,394
Interest expense	744	691
Basis differences in fixed and intangible assets	225	230
Total gross deferred tax assets	17,265	21,565
Less: Valuation allowance	(16,797)	(21,138)	$ (19,929)
Deferred tax assets, net	468	427
Deferred tax liabilities:
Financing and acquisition-related liabilities	(336)	(338)
Indefinite lived assets	(396)	(334)
Deferred tax liabilities, net	(732)	(672)
Net deferred tax liabilities	$ (264)	$ (245)

Income Taxes - Change In Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Changes In The Valuation Allowance For Deferred Tax Assets [Roll Forward]
Valuation allowance at the beginning of the year	$ 21,138	$ 19,929
Decreases recorded as benefits to income tax provision	(4,341)	0
Increases recorded to income tax provision	0	1,209
Valuation allowance at the end of the year	$ 16,797	$ 21,138

Related Parties (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2018	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Issued during period (in Shares)			816,356
Common stock options, exercise price (in dollars per share)			$ 13.99
Board Member \| Consulting services
Related Party Transaction [Line Items]
Expenses incurred with related party (bi-weekly rate)	$ 5		$ 130	$ 126
Issued during period (in Shares)		544
Common stock options, exercise price (in dollars per share)		$ 0.367
Stock options, vesting period			3 years
Chief Scientific Officer \| License Agreement
Related Party Transaction [Line Items]
Royalty obligation, percent of net sales			5.00%
Milestone obligation			$ 600

401(k) Plan (Details) - USD ($) $ in Thousands	12 Months Ended
401(k) Plan (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Qualified employee compensation, employer matching contribution, percent of employees' gross pay	3.00%	3.00%
Qualified employee compensation contribution, amount	$ 400	$ 400

Subsequent Events (Details) - Subsequent Event - USD ($)	Mar. 25, 2020	Jan. 01, 2020	Feb. 28, 2021
1261 Suite A Lease
Subsequent Event [Line Items]
Operating lease, monthly base rent	$ 12,724
Operating lease, annual increase in base rent payment percentage	3.00%
1221 Lease Extension
Subsequent Event [Line Items]
Operating lease, monthly base rent	$ 19,000
Operating lease, increase (decrease) in monthly base rent	600
1261 Suite B/C Lease Extension
Subsequent Event [Line Items]
Operating lease, monthly base rent	$ 16,308.57		$ 17,325
Operating lease, annual increase in base rent payment percentage	3.00%
Employee Stock Purchase Plan
Subsequent Event [Line Items]
Stock options, grants in period, net of forfeitures (in shares)		290,000

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 3,086,000