Note 5 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and equipment, gross	$ 1,133	$ 990	$ 927
Less accumulated depreciation	(923)	(845)	(758)
Property and equipment, net	210	145	169
Computer Equipment and Software [Member]
Property and equipment, gross	127	119	106
Laboratory and Manufacturing Equipment [Member]
Property and equipment, gross	550	481	447
Furniture and Fixtures [Member]
Property and equipment, gross	55	55	48
Leasehold Improvements [Member]
Property and equipment, gross	332	332	326
Construction in Progress [Member]
Property and equipment, gross	$ 69	$ 3

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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