Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (40,796)	$ (31,536)	$ (27,019)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	3,009	1,352	482
Inventory valuation adjustment amortization	611
Stock-based compensation expense	6,388	4,884	2,168
Non-cash interest expense	89	170	238
Loss (gain) on disposal of fixed assets	140	(14)
Change in fair value of preferred stock warrants			90
Changes in operating assets and liabilities:
Accounts receivable	(3,365)	(983)	(1,682)
Prepaid expenses and other assets	289	(1,828)	(273)
Inventory	(3,447)	(1,603)	(2,043)
Other non-current assets	(21)	267
Accounts payable	621	1,318	1,003
Accrued compensation and benefits, other accrued expenses and other current liabilities	822	1,101	2,035
Contract acquisition costs	336
Other non-current liabilities	9,845
Deferred revenue	(708)	(1,849)	2,895
Net cash used in operating activities	(26,187)	(28,721)	(22,106)
Investing activities
Purchases of property and equipment	(10,847)	(1,518)	(1,132)
Purchase of investments		(150)
Acquisition of UmanDiagnostics AB, net of cash acquired	(14,529)	(3,801)
Proceeds from sale of assets		15
Net cash used in investing activities	(25,376)	(5,454)	(1,132)
Financing activities
Proceeds from sale of preferred stock, net of issuance costs			65,575
Proceeds from sale of common stock, net of issuance costs		(20)	8,423
Proceeds from exercise of stock warrants			29
Proceeds from stock options exercised	2,820	1,871	202
Proceeds from ESPP purchase	879
Proceeds from the issuance of notes payable and warrants, net of issuance costs			(59)
Payments on notes payable	(50)	(1,929)	(921)
Net cash provided by (used in) financing activities	116,197	(78)	73,249
Net increase (decrease) in cash and cash equivalents	64,634	(34,253)	50,011
Effect of foreign currency exchange rate on cash	118
Cash, restricted cash, and cash equivalents at beginning of period	45,429	79,682	29,671
Cash, restricted cash, and cash equivalents at end of period	110,181	45,429	79,682
Supplemental cash flow information
Accretion of preferred stock to redemption value			4,110
Cash paid for interest	656	606	743
Warrants issued to lenders			119
Purchases of property and equipment included in accounts payable	164	78
191,152 shares of common stock issued in connection with the acquisition of UmanDiagnostics AB	5,468
Purchases of property and equipment included in other non-current liabilities	7,572		74
Fair value of common stock warrants exercised and reclassified as shares of common stock		196	2,187
Reconciliation of cash, cash equivalents, and restricted cash:
Total cash, cash equivalents, and restricted cash	110,181	$ 45,429	$ 79,682
At-the-market offering
Financing activities
Proceeds from sale of common stock, net of issuance costs	48,019
Underwritten public offering
Financing activities
Proceeds from sale of common stock, net of issuance costs	$ 64,529