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At ASM Microbe, Clinical Microbiologists Question How to Implement FDA's LDT Rule

ATLANTA – The US Food and Drug Administration's recently announced final rule on the regulation of laboratory-developed tests (LDTs) has raised numerous questions among clinical microbiologists about how it will affect their labs and the tests they offer.

In May, the FDA issued a final rule in which it said that LDTs are in vitro diagnostics (IVDs) and that, as all IVDs are medical devices, they fall under the FDA's regulatory umbrella. The agency had long argued that it had such oversight authority, but that it exercised "enforcement discretion." That policy, the agency now says, is no longer appropriate, as IVDs have become more complex and widespread, and are now often a crucial part of patient diagnoses and, as such, are in need of oversight.

This has left clinical microbiologists, many of whom run LDTs in their labs, wondering whether their tests are subject to this regulation, how to implement the rule if they are, and how much that implementation will cost, as many noted during a Saturday session at ASM Microbe, the annual meeting of the American Society for Microbiology (ASM).

"We need clarification and just really additional detail on a lot of these questions," Linoj Samuel, head of the clinical microbiology division at Henry Ford Health and chair of ASM's clinical and public health microbiology committee, said during a session on the FDA's LDT rule.

When proposed, the rule drew criticism from labs and providers. Many argued that its implementation would negatively affect patients' ability to access testing and, in turn, their care, as well as disrupt lab operations as labs grapple with new regulatory requirements. The American Clinical Laboratory Association (ACLA) sued the FDA last month, challenging the agency's authority to oversee LDTs.

Allen Segal, chief strategy and public affairs officer at ASM, said during the session that the society is "seriously looking" into how it may support ACLA in its suit, though he noted that "no final determination has been made."

In response to an audience question, Segal acknowledged that it is widely accepted that some LDT regulation is needed. But, he argued that the solution from the FDA is disproportionate to the problem and it needs to be brought "into better alignment."

Segal outlined three pathways to challenging the rule, including through legal means such as the ACLA suit, but also through a legislative approach and through engaging the FDA itself.

According to Segal, few lawmakers on Capitol Hill are fans of the change the FDA has announced and legislation — like the Verifying Accurate Leading-edge IVCT Development (VALID) Act — could be an alternative approach to LDT regulation. However, in addition to VALID already having failed to pass Congress in 2022, he noted a legislative approach would unlikely lead to a swift change and may rest in part on the outcomes of November's elections.

The third approach focuses on encouraging the FDA itself to modify its own rule. Segal urged clinical microbiologists to ask questions about how to implement the rule, not only to get the answers they need in order to do so in their labs but also to help ASM raise reasonable issues regarding the rule with the agency and then influence changes it may make.

He further noted that there is widespread agreement that the FDA doesn't have the capacity or resources to implement the rule as-is.

"Part of our job is to make sure that FDA knows that and that we're raising these questions," Segal said.

While the rule broadly says the FDA has the oversight to regulate LDTs in the same way as IVDs, the agency has included a number of carve-outs and exemptions, though those too have raised questions among clinical microbiologists.

In the final rule, the agency said it will continue to exercise enforcement discretion for LDTs that were on the market before that final rule was issued, and it would further exercise enforcement discretion for LDTs that have been approved by New York state's Clinical Laboratory Evaluation Program. But if any significant changes are made to existing tests, then they could become subject to the new rule, according to Henry Ford's Samuel.

There are additional carve-outs for tests for rare disease and other areas of unmet need, as well as for health emergencies. But as Samuel noted, some of the exceptions are currently vague.

For instance, an LDT for a rare disease may be exempt because there is currently no FDA-approved test in that area. But what happens, Samuel asked, if a test later becomes FDA approved? Is the previously exempt LDT no longer exempt? He also noted that the carve-out for emergencies does not specify if it is only for national public health emergencies or if local or regional diseases also qualify.

He added that the agency expects to issue further guidance.

Cost is also a consideration for clinical microbiology labs. Michelle Tabb, CSO at Diasorin, which manufactures IVDs, outlined the validation and other studies her company has had to perform to bring IVDs to market. She noted that any claim a company makes on a label — including, for instance, instructions for use and expiration dates — must be backed up with clinical data. All this clinical testing, she said, is costly.

The panel estimated industry costs for testing and validation might be hundreds of thousands of dollars per test, but said the specific requirements for labs are not yet clear.

"What we need to find is really a common goal around here and come to some reasonable solution that that benefits not just us but our patients, as well," Samuel said.