Lab Matters Summer 2025 | Page 31

FOOD SAFETY

By Allison Gennety, specialist, Food Safety

A colorized scanning electron micrograph of Salmonella typhimurium bacteria under 12,000X magnification. Photo: CDC / Bette Jensen.

For over a decade, culture-independent diagnostic tests( CIDTs) have steadily reshaped how clinical and public health laboratories detect pathogens. While their speed and low cost are beneficial for rapid diagnoses and patient management, longstanding concerns about their variability and impact on public health have persisted.

Aside from not having cultured isolates for disease surveillance and outbreak detection, performance is also an issue. Variability in test sensitivity and cross reactivity has led to false positives and low confirmation rates for various organisms in both clinical and public health laboratories. Performance issues undermine patient treatment decisions and appropriate public health response, as well as stress laboratory time and limited resources when staff search for organisms that are not truly there.

APHL and its members have been monitoring this issue over the past several years, and significant progress has been made toward addressing false positive concerns in collaboration with clinical laboratory and industry partners.

These efforts have led to improvements in test accuracy for pathogens like Cryptosporidium and Norovirus, and similar work is underway with Vibrio spp and Campylobacter spp.

In addition to pathogen-specific efforts, APHL recently published a CIDT Fact Sheet that outlines steps public health laboratories, clinical laboratories, federal partners and manufacturers can take to monitor CIDT performance and address issues. Some suggested steps include:

• Ensuring that public health laboratories have clear lines of communication with partners; manufacturers and clinical laboratories are encouraged to do the same;

• Monitoring confirmation rates in real time;

• Encouraging clinical laboratories to submit isolates or clinical material to their public health laboratory for robust disease surveillance; and

• Encouraging public health and clinical laboratories to report discrepancies or abnormal CIDT results to the manufacturer and to FDA MedWatch.

Beyond the technical fixes, APHL is also working on helping strengthen other aspects of usage to support public health laboratories in this CIDT era. This includes ensuring there are accurate resources and training supplies around CIDT related challenges through actions such as webinars. APHL has also updated CIDT survey data from targeted member surveys to see how laboratories are dealing with CIDTs, keeping members informed, identifying gaps and recommending best practices. APHL and its members are also producing documents to streamline bacterial isolate recovery more efficiently and cost effectively from CIDT positive specimens, starting with Salmonella.

As the public health community keeps up with increased CIDT-positive sample submission and false positive events, APHL will continue to provide resources and training to help members stay up to date on the latest information involving CIDTs. The challenges are evolving, but so are the solutions. g