FDA LDT Final Rule (2024)

Since the FD&C Act's 1976 Medical Device Amendments, FDA has asserted authority over IVDs but has exercised 'enforcement discretion' over Laboratory Developed Tests — tests designed, manufactured and used within a single CLIA-certified high-complexity laboratory. The 2024 final rule does not change the legal status (FDA's view has always been that LDTs are devices); it ends the enforcement discretion.

The mechanism is a single amendment to 21 CFR § 809.3 adding 'including when the manufacturer of these products is a laboratory' to the IVD definition, plus a five-stage phaseout schedule published in the preamble.

An LDT lawfully on the market when Stage 4 or 5 applies may continue while a premarket submission is under review, provided the submission is filed by the relevant date.

• 1976-grandfathered LDTs (in clinical use before the 1976 amendments) — continued discretion for premarket review and most QSR requirements.
• Human Leukocyte Antigen (HLA) tests designed, manufactured and used within a single laboratory for transplantation.
• Forensic LDTs used for law-enforcement purposes.
• LDTs used solely within the Veterans Health Administration or the Department of Defense.
• LDTs for unmet needs in integrated health systems where there is no FDA-authorised IVD that meets the need.
• Currently marketed (pre-rule) LDTs that meet specified criteria — continued discretion for premarket review but not for the earlier stages.

Two lawsuits were filed in 2024 challenging FDA's statutory authority to regulate LDTs as devices — most prominently American Clinical Laboratory Association v. FDA. Labs should track these proceedings but plan as if the rule will stand: the agency has continued to publish guidance and is staffing for the phaseout. Stage 1 (MDR) takes effect regardless of mid-litigation posture unless a court issues a stay.

1. Inventory every LDT currently in clinical use, with intended use, target population, performance characteristics and risk classification.
2. Determine carve-out eligibility for each LDT — the answer drives the obligations.
3. Stand up MDR processes by 6 May 2025: complaint intake, severity triage, 30-day/15-day MDR submission workflows, correction & removal reporting.
4. Register the establishment and list each LDT by 6 May 2026.
5. Build the QMS to ISO 13485-equivalent depth by 6 May 2027 — design controls, document control, CAPA, supplier controls, equipment and process validation.
6. Identify Class III LDTs and file PMA/De Novo by 6 November 2027.
7. File 510(k) or De Novo for Class II/I LDTs by 6 May 2028.
8. Establish a sustaining model — design-change control, post-market surveillance, vigilance.

Stage 3 is the largest operational change. CLIA labs run rigorous quality systems but to a different framework: CLIA prescribes analytic validation, proficiency testing, personnel qualification and quality control, but not design controls, design history files, formal CAPA with effectiveness checks, or supplier qualification at the depth FDA QSR/QMSR requires. The 2026 QMSR rewrite of 21 CFR Part 820 — which incorporates ISO 13485:2016 by reference — is now the applicable framework.

Multi-region labs already navigating EU IVDR will recognise the pattern. IVDR ended the previous IVDD self-certification regime, pushed most tests into notified-body review, and brought labs into manufacturer status for in-house IVDs that do not meet the Article 5(5) carve-out. The FDA rule is structurally similar — both regimes assert that laboratory-manufactured tests are devices, both phase out long-standing exceptions, and both require manufacturer-grade QMS.

• Assuming the rule will be vacated and deferring Stage 1 preparation.
• Misreading carve-outs as blanket exemptions.
• Treating CLIA validation packages as substitutes for design verification and validation.
• Underestimating the personnel impact — labs typically need to add regulatory affairs, complaint handling and QA staff.
• Not engaging IDEs early for high-risk LDTs that will need PMA — the 6 November 2027 date is closer than it looks.