U.S. flag An official website of the United States government

U.S. Food and Drug Administration
  1. Home
  2. Medical Devices
  3. Products and Medical Procedures
  4. In Vitro Diagnostics
  5. Laboratory Developed Tests
  1. In Vitro Diagnostics

Laboratory Developed Tests

April 29, 2024: The FDA announced a final rule aimed at helping to ensure the safety and effectiveness of laboratory developed tests (LDTs). The rule amends the FDA's regulations to make explicit that in vitro diagnostic products (IVDs) are devices under the Federal Food, Drug, and Cosmetic Act (FD&C Act) including when the manufacturer of the IVD is a laboratory. Along with this amendment, the FDA is finalizing a policy under which the FDA will provide greater oversight of IVDs offered as LDTs through a phaseout of its general enforcement discretion approach for LDTs over the course of four years, as well as targeted enforcement discretion policies for certain categories of IVDs manufactured by laboratories.

A list of existing resources on device regulation is provided below and the FDA intends to host webinars focusing on specific topics related to the phaseout policy. Additional resources related to the implementation of the phaseout policy will be added to this page as they become available, including information about relevant webinars. Additional information can also be found on Laboratory Developed Tests: Frequently Asked Questions.

On This Page:

Background

Laboratory developed tests, or LDTs, can play an important role in healthcare. LDTs are in vitro diagnostic products (IVDs) that are intended for clinical use and are designed, manufactured, and used within a single laboratory that is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) and meets the regulatory requirements under CLIA to perform high complexity testing.

IVDs are intended for use in the collection, preparation, and examination of specimens taken from the human body, such as blood, saliva, or tissue. LDTs, like other IVDs, can be used to measure or detect a wide variety of substances or analytes in the human body, such as proteins, glucose, cholesterol, or DNA, to provide information about a patient's health, including to diagnose, monitor, or determine treatment for diseases and conditions.

IVDs offered as LDTs are used in a growing number of health care decisions, and concerns about the safety and effectiveness of these IVDs have been raised for many years.

In implementing the Medical Device Amendments of 1976, the FDA generally exercised enforcement discretion for most LDTs, meaning that the agency generally has not enforced applicable requirements with respect to most LDTs. However, the risks associated with most modern LDTs are much greater than the risks associated with LDTs used decades ago. At that time, many LDTs were lower risk, performed in small volumes, and used for specialized needs of a local patient population. Since then, due to changes in business practices and increasing ability to ship patient specimens across the country quickly, many LDTs are now used more widely, for a larger and more diverse population, with large laboratories accepting specimens from across the country. LDTs also increasingly rely on high-tech instrumentation and software, are performed in large volumes, and are used more frequently to help guide critical health care decisions. The FDA is now phasing out the general enforcement discretion approach for LDTs, as discussed below. The phaseout policy is intended to better protect the public health by helping to assure the safety and effectiveness of IVDs offered as LDTs, while also accounting for other important public health considerations such as patient access and reliance.

Increased FDA Oversight to Help Ensure Safety and Effectiveness of LDTs

Due to the evolution and proliferation of LDTs, as well as increasing concerns regarding their safety and effectiveness, the FDA has engaged in discussions regarding increased oversight of LDTs for many years, including holding a workshop in 2010, proposing draft guidance documents in 2014, issuing a discussion paper in 2017, and engaging with congressional and industry stakeholders. Throughout this time, the FDA has maintained that patients and healthcare providers need assurances that the tests they are using are appropriately safe and effective to make good health care decisions. These assurances are lacking for IVDs offered as LDTs without more active FDA oversight. False test results or false claims regarding the meaning of test results can lead to significant patient harm.

On October 3, 2023, the FDA issued a proposed rule aimed at helping to ensure the safety and effectiveness of these IVDs. On April 29, 2024, the FDA announced it had finalized this rulemaking. The final rule amends the FDA's regulations to make explicit that IVDs are devices under the Federal Food, Drug, and Cosmetic Act including when the manufacturer of the IVD is a laboratory. Along with this amendment, the FDA finalized a policy under which the FDA will provide greater oversight of IVDs offered as LDTs through a phaseout of its general enforcement discretion approach for LDTs over the course of four years. The phaseout includes targeted enforcement discretion policies for certain categories of IVDs manufactured by laboratories.

Phaseout Policy

As discussed in the phaseout policy, following a four-year period, IVDs offered as LDTs generally will be expected to meet applicable requirements, though certain IVDs may fall within targeted enforcement discretion policies, as discussed below.

The phaseout policy contains the following five stages:

  • Stage 1: beginning on May 6, 2025, which is 1 year after the publication date of the final LDT rule, FDA will expect compliance with medical device reporting (MDR) requirements, correction and removal reporting requirements, and quality system (QS) requirements regarding complaint files.
  • Stage 2: beginning on May 6, 2026, which is 2 years after the publication date of the final LDT rule, FDA will expect compliance with requirements not covered during other stages of the phaseout policy, including registration and listing requirements, labeling requirements, and investigational use requirements.
  • Stage 3: beginning on May 6, 2027, which is 3 years after the publication date of the final LDT rule, FDA will expect compliance with QS requirements (other than requirements regarding complaint files which are already addressed in stage 1).
  • Stage 4: beginning on November 6, 2027, which is 3½ years after the publication date of the final LDT rule, FDA will expect compliance with premarket review requirements for high-risk IVDs offered as LDTs (IVDs that may be classified into class III or that are subject to licensure under section 351 of the Public Health Service Act), unless a premarket submission has been received by the beginning of this stage in which case FDA intends to continue to exercise enforcement discretion for the pendency of its review.
  • Stage 5: beginning on May 6, 2028, which is 4 years after the publication date of the final LDT rule, FDA will expect compliance with premarket review requirements for moderate-risk and low-risk IVDs offered as LDTs (that require premarket submissions), unless a premarket submission has been received by the beginning of this stage in which case FDA intends to continue to exercise enforcement discretion for the pendency of its review.

The FDA also intends to exercise enforcement discretion and generally not enforce some or all applicable requirements for certain categories of IVDs manufactured by a laboratory, as summarized in the table below. Some IVDs may fall into more than one enforcement discretion policy. We note that an IVD is not excluded from an enforcement discretion policy in the preamble to the final rule simply because it falls within another enforcement discretion policy in such preamble, and so either policy may apply. As noted in the preamble to the final rule, the targeted enforcement discretion policies included in the preamble do not apply to any IVD identified in section V.A.2 as falling outside the scope of the phaseout policy (e.g., donor screening tests for infectious diseases and certain blood typing tests, Direct-to-Consumer tests) or as discussed in section V.B of the preamble.

The table below is intended to provide a high-level overview of certain key categories of IVDs covered in the preamble to the final rule. This table does not address all IVDs (e.g., tests for 564 declarations1). Please refer to the preamble to the rule for additional details and policies.

Category of IVD

Stage 1
Adverse Event Reporting
(21 CFR pt. 803)

Reporting of Corrections and Removals
(21 CFR pt. 806)

Complaint Files
(21 CFR 820.198)

Stage 2
Requirements Not Covered In Other Stages, Including:
Establishment Registration & Device Listing
(21 CFR pts. 607, 807 subpts. A-D)

Labeling
(21 CFR pts. 801, 809)

Investigational Use Requirements
(21 CFR pt. 812)

Stage 3
Quality System Requirements Other than Complaint Files
(21 CFR pt. 820 other than 21 CFR 820.198)

(For LDTs,1 FDA generally will not expect compliance with quality system requirements other than design controls, purchasing controls, acceptance activities, CAPA, and records requirements)

Stages 4 & 5
Premarket Review
(21 CFR pt. 807, subpt. E; 21 CFR pt. 860, subpt. D; 21 CFR 814; 21 CFR pt. 601)

Donor screening tests for infectious diseases and certain blood typing tests

Section V.A.2.a of preamble

compliance currently expected compliance currently expected compliance currently expected compliance currently expected

Direct-to-Consumer (DTC) tests

Section V.A.2.c of preamble

 compliance currently expected compliance currently expected compliance currently expected compliance currently expected

Public Health Surveillance tests

Section V.A.2 of preamble

 compliance generally not expected compliance generally not expected compliance generally not expected compliance generally not expected

1976 type LDTs

Section V.B.1 of preamble

 compliance generally not expected compliance generally not expected compliance generally not expected compliance generally not expected

HLA tests for transplantation

Section V.B.1 of preamble

 compliance generally not expected compliance generally not expected compliance generally not expected compliance generally not expected

Forensic tests

Section V.B.1 of preamble

 compliance generally not expected compliance generally not expected compliance generally not expected compliance generally not expected

DoD and VHA LDTs

Section V.B.1 of preamble

 compliance generally not expected compliance generally not expected compliance generally not expected compliance generally not expected

LDTs for unmet needs by labs integrated in the healthcare system treating the patient

Section V.B.3 of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026

compliance with 21 CFR 820.180-820.186 generally expected beginning May 6, 2027;

compliance generally not expected with other QS requirements (except for complaint files)

 compliance generally not expected

Currently marketed IVDs offered as LDTs first marketed prior to rule publication date and not modified beyond scope described in preamble

Section V.B.3 of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026

compliance with 21 CFR 820.180-820.186 generally expected beginning May 6, 2027;

compliance generally not expected with other QS requirements (except for complaint files)

 compliance generally not expected

Nonmolecular antisera LDTs for rare red blood cell antigens

Section V.B.3 of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026

compliance with 21 CFR 820.180-820.186 generally expected beginning May 6, 2027;

compliance generally not expected with other QS requirements (except for complaint files)

 compliance generally not expected

LDTs approved by NYS CLEP2

Section V.B.2 of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026 compliance* generally expected beginning May 6, 2027 compliance generally not expected

Modified version of another manufacturer's 510(k) cleared or De Novo authorized test within the scope described in the preamble

Section V.C.4 of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026 compliance* generally expected beginning May 6, 2027 compliance generally not expected

IVDs offered as LDTs within scope of phaseout policy, but that do not fall within a targeted enforcement discretion policy summarized above

Section V.C of preamble

 compliance generally expected beginning May 6, 2025 compliance generally expected beginning May 6, 2026 compliance** generally expected beginning May 6, 2027

compliance generally expected beginning November 6, 2027 for high-risk tests

compliance generally expected beginning May 6, 2028 for moderate-risk and low-risk tests

1 LDTs are IVDs that are intended for clinical use and that are designed, manufactured, and used within a single laboratory that is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) and meets the regulatory requirements under CLIA to perform high complexity testing.

2 As discussed in the preamble to the final rule, FDA uses the phrase "LDTs approved by NYS CLEP" to refer to LDTs that are approved by, conditionally approved by, or within an approved exemption from full technical documentation under NYS CLEP.

* Because these tests are LDTs, FDA generally will not expect compliance with 21 CFR Part 820 requirements other than design controls, purchasing controls, acceptance activities, CAPA, and records requirements.

** IVDs offered as LDTs that are within the scope of the phaseout policy but that do not fall within a targeted enforcement discretion policy summarized in the table may be an LDT if they are IVDs that are intended for clinical use and designed, manufactured, and used within a single laboratory that is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) and meets the regulatory requirements under CLIA to perform high complexity testing. For tests that are LDTs, FDA generally will not expect compliance with 21 CFR Part 820 requirements other than design controls, purchasing controls, acceptance activities, CAPA, and records requirements.

Webinars

The FDA held a webinar on May 14, 2024, to provide an overview of the final rule and phaseout policy.

The FDA intends to hold additional webinars focusing on specific topics related to the phaseout policy. These will be announced as they are scheduled.

To submit questions to be answered during the webinars, email CDRHWebinars@fda.hhs.gov at least two weeks prior to the webinar.

Medical Device Regulatory Resources

Related Links

Historical LDT Related Links



Subscribe to In Vitro Diagnostics

Sign up to receive email updates on In Vitro Diagnostics.

Back to Top