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What Labs Need to Know About the FDA’s Compliance Timeline for Laboratory-Developed Tests (LDTs)

The landscape for laboratory-developed tests (LDTs) is undergoing significant changes with the FDA’s recent final rule. This move aims to ensure the safety and reliability of LDTs, which play a crucial role in modern healthcare. The FDA has provided a four-year transition period for laboratories to achieve full compliance with the new regulations for laboratory-developed tests (LDTs). This phased approach is designed to allow laboratories sufficient time to adapt to the new requirements while minimizing disruption to patient care.

Here’s a breakdown of the different stages involved in the FDA’s regulation of LDTs and what it means for laboratories and healthcare providers.
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Year 1: Initial Preparations

In the first year, laboratories need to begin preparations for compliance with premarket review and quality system (QS) requirements. This involves:

  • Documentation and Validation: Laboratories must start documenting their processes and validating their tests to meet FDA standards.
  • Modifications and Adjustments: Necessary modifications to existing tests and processes should be identified and implemented to ensure alignment with FDA regulations.

Years 2-3: Phased Enforcement

The second and third years involve continued phased enforcement of the new regulations. During this period:

  • Targeted Enforcement Discretion: The FDA will apply enforcement discretion to specific categories of LDTs. This includes tests developed for unmet medical needs within integrated healthcare systems, tests approved by the New York State Department of Health’s Clinical Laboratory Evaluation Program (NYS CLEP), and tests marketed before the rule’s issuance.
  • Ongoing Adjustments: Laboratories should continue adjusting their operations to meet FDA requirements, ensuring all necessary processes are in place for full compliance by the end of the transition period.

Year 4: Full Compliance

By the end of the fourth year, laboratories must achieve full compliance with all FDA regulations. This includes:

  • Premarket Review: All LDTs must undergo premarket review to demonstrate their safety and effectiveness.
  • Quality System Requirements: Full implementation of QS requirements, including good manufacturing practices, must be in place.
  • Labeling and Reporting: Compliance with labeling, adverse event reporting, and other applicable regulatory requirements must be ensured.


The FDA’s new regulations for LDTs represent a significant shift towards ensuring the safety and effectiveness of these critical diagnostic tools. By defining LDTs as medical devices, introducing phased premarket review and QS requirements, and applying targeted enforcement discretion, the FDA aims to enhance patient safety while maintaining access to vital tests. Laboratories now have a clear timeline and set of requirements to follow, ensuring a smooth transition to the new regulatory landscape. For healthcare providers and patients, this means more reliable diagnostic tests and better-informed healthcare decisions.

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