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The FDA’s proposed rule for LDTs could significantly impact how tests currently exempt from FDA scrutiny are offered.
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U.S. FDA Proposed Rule on Laboratory-Developed Tests

The FDA faces a quandary—increasing oversight of LDTs to protect public health without affecting the quality of patient care

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Erica Conway, PhD

Erica Conway, PhD, has more than twenty years of regulatory affairs and quality assurance experience, primarily within the In Vitro Diagnostic (IVD) medical device field. Conway joined MCRA, a consultancy company, in August 2022 as VP, IVD Regulatory Affairs. Prior to MCRA, Conway’s first industrial experience started in the regulation of pharmaceuticals before moving into clinical trials for medicinal products. Conway moved into the field of IVD medical devices in 2006 for a major diagnostics manufacturer, before becoming an independent consultant, working within the IVD and medical device fields on aspects of regulatory affairs and quality management systems. Latterly, Conway spent 8.5 years as global head of IVDs and the head of IVD Notified Body (NB) at the British Standard Institution (BSI). At BSI, Conway was pivotal in the implementation of the IVD Regulation (IVDR., [EU] 2017/246) and the successful designations of both the UK and the Netherlands organizations to the IVDR. Conway has a bachelor of science (BSc Hons) in physiology from the University of Sheffield, UK; a doctorate of philosophy (PhD) specializing in neurophysiology from the University of Bristol, UK; and completed a short postdoctoral fellowship at the University of Cambridge before joining industry.

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Published:Nov 28, 2023
|3 min read
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As the deadline approaches for public comment, the U.S. FDA’s proposed rule for laboratory-developed tests (LDTs) could significantly impact how, or certainly how many, tests currently exempt from FDA scrutiny are offered.

Since 1976, the FDA has excercised “enforcement discretion” on certain types of assays. At the time, these were low volume tests, often for treating rare diseases, or tests used in local healthcare settings that employed manual techniques performed by specialist laboratory personnel. 

However, during the decades that followed, the breadth, complexity, and volume of LDTs has grown. There has been not only an evolution in the complexity of technology, including the use of algorithms, but also in the tests being offered in large volumes by commercial entities, where samples may be shipped nationwide. 

The extent of LDTs being offered and performed by US institutions is currently unknown.

What is the FDA proposing?

Much has been written over the last few weeks of the proposed FDA Rule that would see the FDA “phase out its general enforcement discretion approach for LDTs, so that IVDs manufactured by a laboratory would generally fall under the same enforcement approach as other IVDs.”

The Proposal, currently subject to consultation until December 4, suggests a phased approach; there would be five stages of phaseout, and therefore five deadlines for laboratories to meet the new requirements:


Deadline (post publication)


Stage 1 1 year Medical device (adverse event) reporting (MDR) requirements would apply, including correction and removal of tests
Stage 22 yearsImplementation of other IVD requirements (e.g., registration); except Quality System and premarket review requirements (covered by Stage 3 onwards)
Stage 33 yearsQuality System requirements
Stage 43.5 years; not before Oct. 1, 2027Premarket review requirements for high-risk IVDs
Stage 54 years; not before April 1, 2028Premarket review requirements for moderate and low risk IVDs (that require submission)

Under the Proposal, some tests would still be allowed to be offered as an LDT. For instance, this phaseout policy would not include “1976-Type LDTs.” However, to understand this possible exemption, we need to understand what the FDA means by 1976-Type LDTs. 

According to an October 31 FDA webinar on the subject, these tests include “LDTs with the following characteristics, which provide the greatest risk mitigation among the characteristics that were commonly associated with LDTs offered in 1976.” 

There are areas of the Proposed Rule that would clearly require more guidance from the FDA, including, which tests would still meet the 1976 (or amended) criteria.

The FDA is requesting feedback—could there be flexibility?

Time is now critical to understand the ramifications of what this Rule would mean to labs and tests being offered under the LDT provision. The FDA is requesting specific feedback, such as from  academic and small labs, on the unintended consequences and the proposed transition provisions. 

Based on the information outlined in the October 31 webinar, there is potential for the FDA to adapt the Proposal while achieving its aim of increasing oversight, e.g., requiring devices to undergo premarket approval while maintaining other stated requirements, or grandfathering certain types of tests that are currently offered. 

The deadline to comment is December 4

The FDA faces a quandary—increasing oversight and safety of LDTs to protect public health without affecting the quality of patient care, which largely relies on labs and diagnostic tests.

The deadline to comment on the Proposed Rule is December 4. If you or your laboratory will be affected by the proposed changes, providing impactful comments could help shape the legislation.  Comments should provide constructive and meaningful feedback supported by objective data. 

Want to comment? Learn more about the specific guidelines for commenting on the Proposed Rule on LDT regulation before December 4.