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Laboratory-developed Tests (LDTs)

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Putting Laboratory Tests into Practice: Part I II III  IV V

Although LDTs are not FDA-approved for marketing, some of the reagents, controls, and equipment used in these tests may be manufactured (and are FDA-approved). The reagents in these instances are called Analyte Specific Reagents, or ASRs. In addition, some tests are developed as proprietary tests. That is, the test is marketed to other labs and health care providers as a service, but samples must be sent to the lab that developed the test for analysis. Examples of such tests include many genetic tests for various cancers. These are usually very complex tests and sometimes involve an algorithm developed by the lab used to evaluate a combination of results. These types of tests are referred to as "In Vitro Diagnositc Multivariate Index Assays" (IVDMIAs). Examples of this type of test are the gene expression tests for breast cancer. Currently, the FDA is looking at whether it should become more involved in the regulation of these types of tests, and the Agency issued a draft guidance on them in July 2007.

It is important to note that once a laboratory has validated a test for in-house use, methods of quality assurance with regard to that test are carefully and continually followed by the laboratory. This means that laboratories must constantly monitor the test and test systems to ensure that results generated continue to be as accurate, precise, sensitive, and specific as originally validated. These processes are also regulated by federal and state governments as well as laboratory accrediting organizations and are examined on a regular basis. For more on this, you may want to visit two other articles on the site:


Continue to the next article in the series: Part IV: Exceptions: Humanitarian Use


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