FDA Reverts Laboratory Developed Tests to Pre-2024 Wording

Sarah Fitzgerald and Evangeline Loh

Background on LDTs

Laboratory Developed Tests (LDTs) are in vitro diagnostic (IVD) tests manufactured and used within a single lab. Since at least 2010, the Food and Drug Administration (FDA) has expressed concerns related to safety, effectiveness and variability of LDTs. 

U.S. LDT Legislation Released May 2024

In May 2024, the FDA released its final rule on LDTs. The final rule phased in additional requirements for many LDTs aligned with general expectations for IVD devices. The FDA characterized this as helping LDTs meet safety and effectiveness expectations.

To support this new rule, the definition of IVD products, 21 CFR §809.3(a), was updated to explicitly indicate that laboratories could be considered manufacturers.

U.S. District Court vacates LDT rule March 2025

In March 2025, the U.S. District Court vacated this rule and remanded the matter to the Secretary of Health and Human Services (HHS) for further consideration. The FDA declined to appeal the ruling.

Definition of in vitro diagnostic products reverted

On Sept. 19, 2025, the FDA published a new rule reverting the text of 21 CFR §809.3(a) to what it was before the May 2024 rule. Specifically, the phrase “including when the manufacturer of these products is a laboratory” was removed.

Concluding remarks 

The FDA estimated that the 2024 LDT rule would have cost between $1.29 billion and $1.37 billion annually and less regulation generally allows greater innovation and faster access. However, the concerns expressed by the FDA still exist. Further, the FDA opines that medical device manufacturers may be disincentivized from developing IVDs that cover the same tests as LDTs.

Therefore, the FDA has enforcement discretion over LDTs, which are regulated by the Centers for Medicare and Medicaid Services (CMS) under the Clinical Laboratory Improvement Amendments (CLIA).

Emergo by UL notes that this is similar to the European Union (EU) IVD regulation (IVDR / Regulation (EU) 2017/746), in which in-house IVDs that are manufactured and used within health institutions, on a non-industrial scale and meet the conditions of Article 5(5) are exempt from most requirements. Specifically, they must comply with General Safety and Performance Requirements (GSPR) Annex I, but do not need to undergo formal conformity assessment procedures.