LAB TO LAB
While most common laboratory tests are commercial tests, manufactured and marketed to multiple labs, some tests are developed, evaluated, and validated within one particular laboratory. These tests, called “laboratory-developed tests” or “LDTs” are used solely within that laboratory and are not distributed or sold to any other labs or healthcare facilities to perform on their own. Often, a lab will choose to develop and use an LDT because a commercial test is not currently available.
There can be several reasons why a commercial test has not been developed for a particular analyte or disease of interest. For example, many LDTs are genetic tests that are developed for rare diseases, such as Huntington disease. These are diseases that only a small subset of the population has, reducing the incentive for a manufacturer to develop a commercial version because the market for such a product would be small and not offer much, if any, return on investment. Or, an existing test may not apply to a particular subpopulation from which the lab has patients, so modification of the test is required. (Any FDA-approved commercial test that is modified in any way by a lab is considered to be an LDT and is subject to the regulations applied to all LDTs.)