Building Reliability Before an Outbreak

Proficiency testing is a cornerstone of external quality assessment, challenging laboratories to analyze unknown samples and compare their results against peer performance. This process provides objective evidence that laboratory methods, instruments, and staff competency meet required standards (Centers for Medicare & Medicaid Services [CMS], 2022).

During routine operations, PT quietly reinforces a laboratory’s diagnostic accuracy. When a crisis occurs, that accumulated assurance translates into confidence and capability. Laboratories with strong PT performance records are better equipped to detect emerging pathogens, interpret unusual results, and communicate reliable data under pressure (Tholen et al., 2006).

Fungal Outbreaks: The Challenge of Candida auris

One of the most pressing examples is Candida auris (C. auris), a multidrug-resistant fungus responsible for persistent healthcare-associated outbreaks. As we discussed in our previous article, “Preparing Laboratories for Emergent Pathogens,” the multidrug-resistant fungus, Candida auris (C. auris), is notoriously difficult to identify with some traditional methods, leading to misidentification and, consequently, unrecognized nosocomial outbreaks. By testing identification methods through PT, laboratories can recognize misidentification issues early, retrain staff, and adjust protocols to spot a potential outbreak within their facility earlier.

Foodborne Disease Surveillance and PulseNet

Bacterial pathogens such as Salmonella and E. coli are frequent culprits in multistate foodborne outbreaks. Through microbiology culture and molecular PT programs, laboratories ensure their serotyping and PCR methods align with standards used by CDC’s PulseNet network. Accurate, comparable data allows public health agencies to trace contamination sources quickly and prevent further spread (Centers for Disease Control and Prevention [CDC], 2024).

COVID-19 and Emerging Respiratory Threats

The COVID-19 pandemic demonstrated the critical role of PT in maintaining consistent testing performance across thousands of new and existing laboratories. Early in the response, PT provided a vital check on assay accuracy and comparability, ensuring data reported to health authorities could be trusted for clinical and policy decisions (CMS, 2020).

Antimicrobial Resistance and Healthcare-Associated Outbreaks

Antimicrobial-resistant organisms—such as carbapenem-resistant Enterobacterales (CRE)—pose an ongoing outbreak risk in healthcare settings. PT participation verifies a laboratory’s ability to detect resistance mechanisms and interpret antimicrobial susceptibility results accurately, directly supporting infection control and antibiotic stewardship (CDC, 2023).

Across these scenarios, PT acts as a real-world test of readiness—ensuring laboratories can deliver accurate results that guide outbreak containment and protect public health.

Supporting Laboratory Competency and Readiness

Staff competency is another critical factor in outbreak management. During emergencies, laboratories experience increased testing volume, staff turnover, and pressure to deliver fast results. PT offers a measurable, objective tool for assessing and maintaining staff proficiency over time. It verifies that even under stress, personnel can correctly interpret complex or unusual results (CMS, 2022).

In addition, PT data contributes to ongoing quality improvement. Laboratories can analyze their performance trends, identify recurring issues, and strengthen internal quality systems—ensuring that response capabilities continue to evolve alongside new technologies and emerging pathogens (Clarke & O’Connor, 2020).

Conclusion

In outbreak management, proficiency testing is both a preventive measure and a performance benchmark. It ensures that laboratories are not simply reacting to crises, but are prepared long before they occur. By validating analytical accuracy, confirming staff competency, and promoting data comparability across networks, PT underpins the diagnostic confidence that drives effective public health response.

Moreover, consistent participation in PT ensures data comparability across hospital systems and public health networks. In outbreak scenarios, where multiple laboratories may test specimens from the same cluster, result harmonization is vital for epidemiological tracing and response coordination (World Health Organization [WHO], 2016). A laboratory’s PT performance assures that its results are not only accurate but also consistent with national and global surveillance standards.

At WSLH Proficiency Testing, we are proud to support laboratories in maintaining this readiness. Each PT event represents more than an exercise—it is an investment in the resilience of our collective public health infrastructure, ensuring that when the next outbreak arises, laboratories are equipped to respond with precision, consistency, and trust.

References

Centers for Medicare & Medicaid Services. (2022, July 11). Clinical Laboratory Improvement Amendments of 1988 (CLIA) proficiency testing regulations related to analytes and acceptable performance. Federal Register, 87(131), 41194–41250. https://www.federalregister.gov/documents/2022/07/11/2022-14513/clinical-laboratory-improvement-amendments-of-1988-clia-proficiency-testing-regulations-related-to

Sunderman, F. W. (1992). The history of proficiency testing/quality control. Clinical Chemistry, 38(7), 1205–1209.

Wisconsin State Laboratory of Hygiene Proficiency Testing. (n.d.-a). About WSLH PT – Quality Laboratory Improvement Since 1966. Retrieved October 23, 2025, from https://wslhpt.org/about-wslh-pt-quality-laboratory-improvement/

Wisconsin State Laboratory of Hygiene Proficiency Testing. (n.d.-b). CLIA and proficiency testing changes. Retrieved October 23, 2025, from https://wslhpt.org/clia-and-proficiency-testing-changes/

Wisconsin State Laboratory of Hygiene Proficiency Testing. (2023). Preparing Laboratories for Emergent Pathogens. WSLH PT Blog. https://wslhpt.org/blog/preparing-laboratories-for-emergent-pathogens/