The FDA made its case for greater regulatory authority over laboratory developed tests (LDTs) in a recent report that details 20 incidents in which the tests were linked with patient harm (http://1.usa.gov/1PL0iot).
Laboratory developed tests are considered a subset of in vitro diagnostics, which the FDA has regulated as medical devices since 1976. In contrast to diagnostic tests made by a conventional manufacturer and used by many laboratories, LDTs are designed, manufactured, and used in a single laboratory.
Voelker R. More Oversight Needed for LDTs. JAMA. 2016;315(1):20. doi:10.1001/jama.2015.17506