Lab-developed test (LDT)

How an LDT differs from a test kit

Some lab tests are sold as kits or instruments that a manufacturer submits to the FDA, and any certified lab can buy and run them. A lab-developed test is different: one laboratory designs it, validates it and performs it in-house, and samples from across the country are shipped to that lab.

LDTs are common for newer, rarer or more specialized questions where no commercial kit exists. Examples include many genetic panels, some hormone metabolite profiles and several multi-marker screening tests.

Who oversees them

Under the Clinical Laboratory Improvement Amendments (CLIA), run by the Centers for Medicare & Medicaid Services, every U.S. lab testing human samples for health purposes must be certified and meet quality standards that scale with test complexity. CLIA focuses on how the lab operates, including staff qualifications, quality control and proficiency testing.

In May 2024 the FDA finalized a rule that would have phased in FDA oversight of LDTs as medical devices. A federal district court vacated that rule on March 31, 2025, and on September 19, 2025 the FDA issued a rule restoring the regulation to its prior text. For now, most LDTs reach patients without FDA premarket review.

What that means for you

CLIA certification tells you the lab meets operating standards. It does not, by itself, show that a particular test reliably predicts a health outcome or that acting on it improves your health. That second question, clinical validity and usefulness, is where published evidence matters.

• What is this test intended to detect, and in whom was it studied?
• How often does it give false positives or false negatives?
• Has it been compared with an established reference method?
• Would the result change what my clinician recommends?

Reference ranges can differ

Because each lab builds its own method, results from one LDT are not always comparable with another lab's version of a similar test. Compare your result with the range on your own report, and use the same lab when tracking change over time.

How HealifyMD approaches specialty tests

HealifyMD offers some specialty panels alongside standard blood work. Before you order, your clinician can explain whether a test is lab-developed, what it can and cannot tell you, and whether a standard test would answer the same question. Specialty tests are priced separately and listed on each test page.