Laboratory-developed tests (LDTs) gained significant attention during the early stages of the COVID-19 pandemic to meet the urgent demand for testing. One of the key advantages of LDTs compared to traditional diagnostic tests is the expedited approval process. While conventional diagnostic tests often require years to navigate through research, development, clinical trials, manufacturing setup, and regulatory review by agencies like the U.S. Food and Drug Administration (FDA), LDTs are typically designed to obtain clearance and be regulated for use within just a few months.
The FDA defines LDTs as in vitro diagnostic tests (IVDs)—meaning tests performed outside the body, typically in a lab setting—that are designed, manufactured, and used within a single laboratory. These are often referred to as “in-house” or “home brew” tests. The question of the FDA’s authority to regulate LDTs has been a longstanding and complex debate. Historically, the FDA has allowed oversight of LDTs to fall under the Clinical Laboratory Improvement Amendments (CLIA), as these tests were originally simple and used on a limited scale.
However, with advancements in technology, LDTs have become more sophisticated, widely used across the country, and potentially pose greater risks to patient safety if not properly validated. The FDA argues that inaccurate LDT results could lead to harmful outcomes, such as unnecessary treatments or missed diagnoses, which may result in serious illness or death. On the other hand, many clinical laboratories believe that LDTs are already adequately regulated under CLIA, and that additional FDA oversight would amount to redundant regulation.
“LDTs fill a void where there is no FDA-approved test. We need to be able to build these things with a healthy amount of regulation, but not a burdensome amount. … If labs had to go through premarket review for all LDTs, it would make the assays more expensive to run, and I think a lot of laboratories would just throw in the towel.”
– Dennis Dietzen, PHD, Professor of Pathology and Immunology, Washington University
On May 6, 2024, the FDA finalized a rule intended to strengthen the safety and effectiveness of LDTs. This rule updates the FDA’s regulations to clearly state that IVDs are considered medical devices under the Federal Food, Drug, and Cosmetic Act (FD&C Act), even when they are developed and used within a laboratory setting. Additionally, the FDA is implementing a phased approach to increase oversight of IVDs offered as LDTs. Over a four-year period, the agency will gradually phase out its longstanding policy of general enforcement discretion for LDTs, while also applying specific enforcement policies to certain categories of lab-manufactured IVDs.
On March 31, 2025, a Texas judge for the U.S. District Court for the Eastern District of Texas issued a ruling that overturned the FDA’s final rule on LDTs as medical devices. This struck down the FDA’s final rule, issued in April 2024, asserting that LDTs must follow stricter standards and be regulated by the FDA. This final rule was set to be phased in, beginning in May of 2025. However, the FDA’s ruling was met with significant pushback by key players in the lab industry.
Industry groups who strongly opposed the FDA’s final rule included the American Clinical Laboratory Association (ALCA) and the Association for Molecular Pathology (AMP). These groups argued that the FDA’s regulation of LDTs as medical devices would impose undue burdens on laboratories and stifle innovation in diagnostic testing. The American Medical Association also noted that this regulation could result in the loss of “many critical tests and stifle innovative advances.”
“The court’s ruling ensures that clinical laboratories can continue to focus on their primary mission—offering innovative and reliable diagnostics that save and improve the lives of millions of patients every day. This is a victory that protects patient access to critically needed testing services and removes burdensome regulations that would have undermined the clinical laboratory system in this country.”
– Susan Van Meter, President, American Clinical Laboratory Association
The Judge ruled that CLIA had sufficient oversight of LDTs already and the FDA lacked the authority to regulate them. However, the court’s decision leaves open the possibility of future regulatory action, either through a successful appeal of the order or other regulatory action. While advocates argue that reduced oversight could accelerate innovation and broaden access to cutting-edge testing, critics caution that it may compromise patient safety and diagnostic accuracy.
As the legal and regulatory frameworks continue to shift, it will be crucial for policymakers, laboratories, and healthcare providers to strike a careful balance, ensuring both the advancement of diagnostic science and the protection of public health. The implications of this decision will likely ripple through the industry for years to come, shaping how LDTs are developed, validated, and trusted in clinical care.
To learn more about LDTs, read this in-depth overview from the VMG Health team.
