Op-Ed: Proposed LDTs Rule Threatens Outbreak Containment

March 18, 2024

Across America, clinical and public health laboratories are at the front lines of discovery—and warning—for the world's next pandemic. Armed with laboratory-developed tests (LDTs) to assess fast-moving outbreaks, these labs can move at the speed of science, saving lives and sounding alarm bells for the community and the country. Used for more than a decade, LDTs can help diagnose influenza, screen for genetic disorders and test for cancer. They're at the front lines of detection for mosquito-borne illnesses like the West Nile virus. And they can bolster rapid diagnosis of infectious diseases like and , or track the Pneumocystis jirovecii organism that .

No one needs reminding of what a global outbreak looks like. But you might not realize how many regional infections lurk beneath the surface. Just 2 years ago, West Nile virus in America's worst-ever outbreak, amid . With the to shift the geographic boundaries of infectious diseases—from West Nile virus to tick-borne diseases like Lyme disease—we need LDTs more than ever.

Yet new federal regulations under consideration could hinder their effectiveness.

The Food and Drug Administration (FDA) recently proposed a rule that would require the same premarket approval for LDTs as it does for medical devices, such as prosthetic joints or pacemakers. The potential rule could bring significant harm to patients by limiting the clinical microbiology and public health laboratories that serve them. The medical device pathway under consideration is designed for commercially developed medical devices. It's ill-suited to regulate LDTs, and it's especially at odds with the realities of infectious disease testing. If adopted, the FDA's rule will disincentivize clinical and public health labs from developing and deploying essential LDTs. It will create gaps in diagnosis and care, and it could potentially impact underserved communities the most.

Unevenly Distributed Impacts

We've seen firsthand how each minute matters when testing for infectious diseases. For example, thanks to the use of LDTs on 1 patient, we determined within hours that bacteria resistant to multiple drugs had caused a life-threatening infection. We intervened with the right antibiotic almost immediately—a process that would have extended another day or 2 had we used routine diagnostic methods. Such differences in response time can be critical to survival.

Delays in test results can also fuel outbreaks, with infections quickly spreading to others in the same hospital or community. Amid labs already and declining reimbursement rates, the FDA's proposed rule adds onerous new requirements, including a new user fee that places undue burden on laboratory staff. If this rule forces local labs—directly integrated into the care of patients through hospitals—to discontinue testing within their own facility, access to timely care becomes even more difficult. This could have an enormous impact on patients in rural or underserved communities, who may face substantial delays to get their test results.

Consider some additional possibilities. The P. jirovecii fungus referenced earlier can cause , a serious fungal infection affecting the lungs, especially among those with compromised immune systems. Clinicians have used LDTs to diagnose the infection for more than a decade, as it's 1 of many pathogens with no FDA-approved tests. If the new rule is put in place, it will introduce a costly, time-consuming regulatory process that could lead to clinical and public health labs—especially small ones—abandoning tests for these pathogens altogether. This, in turn, will limit patient access and create gaps in care.

Those gaps would not be evenly distributed. Take Arizona, where certain regional diseases rely heavily on LDTs to protect public health. The state has one of the largest Native American populations in the U.S., many of them residing in remote rural settings. These areas experience endemic infectious diseases like hantavirus and coccidiomycosis, potentially fatal conditions that require rapid diagnosis—often through LDTs.

Increased Importance Ahead

Market and environmental developments suggest LDTs will matter more, not less, in the years to come. The perfect storm of conditions that allowed the rapid spread of West Nile virus in central Arizona can also affect other mosquito-borne diseases, like dengue virus and malaria in Florida—and no FDA-approved molecular assay exists for the diagnosis of any of these pathogens. The Zika virus, another mosquito-borne disease, lacks an FDA-approved molecular assay. And M. tuberculosis just recently had the only FDA-approved molecular test for rapid identification from positive patient cultures pulled off the market.

From tuberculosis to dengue to malaria, we have no option but to use LDTs to detect pathogens of major public health importance. In the era of growing antimicrobial resistance, our reliance on LDTs to detect highly antibiotic-resistant superbugs will only increase.

The FDA's proposed rule will erode our capacity to respond to emerging pathogens or even the next pandemic—and it will come at a time when we need more, not less, front-line innovation. In our work, we've long seen LDTs at the leading edge of patient care, whether it's life-or-death diagnoses, outbreak containment or access to testing.

We believe the FDA has an important role to play in monitoring and regulating LDTs, but this rule is the wrong approach. It's simply not a practical solution, especially for infectious disease tests. If the rule takes effect, it will gravely impact access to care by postponing test results, limiting patient access and delaying critical warnings for the next pandemic. With of human pathogens globally, this rule could ultimately threaten public health.

We must find a middle ground for regulating LDTs that allows clinical microbiology and public health laboratories to continue performing them for infectious diseases. Such capabilities are essential to control outbreaks and ensure patient access to life-saving treatment.