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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 healthcare 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 Diagnostic 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 exercise its legal right to oversee the regulation of these types of tests. In 2014, the agency informed Congress of its plans to develop a new, draft risk-based approach for overseeing moderate and high-risk LDTs that would phase in over a period of years.

FDA took steps that included posting draft guidance documents on its website and publishing notices in the Federal Register to formally announce the release of this material and asking for public comments. The agency says increased oversight of the tests is warranted, due to the potential risk some LDTs pose to consumers. In November 2015, the agency issued a report highlighting twenty case studies where LDTs may have or actually caused harm to patients.

It is the agency's intent to release final guidance on LDT oversight later in 2016, although some industry groups and members of Congress oppose the idea of giving FDA more oversight over LDTs. Their argument is this proposal would create more administrative burdens and ultimately discourage the use of these tests.

Instead, they are calling for alternative approaches that would build upon the existing CLIA framework. As of now, the CMS is the federal agency responsible for ensuring the accuracy and quality of these tests.

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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