There are two routes to developing and commercializing a clinical diagnostic assay: submitting a test for FDA approval, or conducting an internal validation to create a laboratory-developed test which is commonly known as a home-brew test.
Through the first route, there are two options: either the premarket approval (PMA) process, or 510(k) premarket notification that is based on a comparison to a predicate device. While these options allow a test to be sold to licensed reference laboratories in the United States, the process can be slow, expensive, and time-consuming. This route is required for high-volume products which are intended for manufacture and sale to third-party laboratories.
The second route is routinely undertaken by clinical laboratories and involves in-house internal assay validation. IVD tests developed and validated internally are indeed considered medical devices, and are created utilizing general-purpose reagents and analyte specific reagents (ASRs). In 1996, FDA introduced regulations that outline how ASRs and general-purpose reagents should be used to develop home-brew assays.
Code of Federal Regulations, 21 CFR 864.4020.