Laboratory developed tests are not FDA regulated--never have been--instead the labs are regulated under the Clinical Laboratory Improvement Amendments (CLIA) as overseen by the CMS. Laboratory developed tests are the kind your doctor orders, they are a service not a product and are not sold directly to patients. Labs develop new tests routinely and they do not apply to the FDA for approval. Despite this long history, the FDA has claimed that it has the right to regulate lab tests and they have merely chosen not to exercise this right for forty years. In 2015, Paul Clement the former US Solicitor General under George W. Bush and Laurence Tribe, considered by many to be the leading constitutional lawyer in the United States, wrote an article that rejected the FDA's claims writing that the “FDA’s assertion of authority over laboratory-developed testing services is clearly foreclosed by the FDA’s own authorizing statute” and “by the broader statutory context.”
Despite lacking statutory authority, the FDA has continued to claim it is authorized to regulate laboratory tests. Indeed, a key failure in the pandemic happened when the FDA issued so-called "guidance documents" saying that any SARS-CoV-II test had to be pre-approved by the FDA. Thus, the FDA reversed the logic of emergency. In ordinary times, pre-approval was not necessary but when speed was of the essence it became necessary to get FDA pre-approval. The FDA's pre-approval process slowed down testing in the United States and it wasn't until after the FDA lifted its restrictions in March that tests from the big labs became available.
Clement and Tribe rejected the FDA claims of regulatory authority over laboratory developed tests on historical, statutory, and legal grounds but they also argued that letting the FDA regulate laboratory tests was a dangerous idea. In a remarkably prescient passage, Clements and Tribe (2015, p. 18) warned:
Clement and Tribe nailed it. Catastrophic delays, with disastrous consequences for patient care is exactly what happened.