Organization of External Quality Control Testing for Plague Using Encrypted Sample Panels

The aim of the work was to evaluate the results of external quality control of molecular-genetic and immunological testing for plague in anti-plague laboratories using encrypted control panels. Materials and methods. A total of 19 anti-plague institutions participated in the external quality control program. The quality of laboratory testing was assessed using polymerase chain reaction (PCR) and fluorescent antibody method (FAM) with encrypted panels, in which the composition of samples was unknown to the participating laboratories. The PCR panels contained dried DNA preparations of Yersinia pestis EV NIIEG strain as positive samples, as well as DNA of Yersinia pseudotuberculosis and Escherichia coli at concentrations of at least 1 ng and a 15 % sucrose solution as negative samples. For assessment of plague detection applying fluorescent antibody method, fixed smears of the same microorganisms (Y. pestis EV NIIEG, Y. pseudotuberculosis and E. coli) were used at concentrations of 1·10⁶ microbial cells per milliliter. Results and discussion. The analysis of external quality control results obtained from anti-plague laboratories was performed over the period of 2011–2025. The proportion of false-positive results obtained through FAM was 0.7 %, while false-negative results accounted for 0.47 %. In PCR-based detection, false-positive results accounted for 1.27 % and false-negative results for 0.36%. The analysis made it possible to identify potential sources of analytical errors in plague detection and to determine measures aimed at their elimination. To prevent erroneous results, it is necessary to implement internal quality control procedures, ensure timely procurement of diagnostic reagents, maintain proper condition of laboratory equipment, strictly follow manufacturers’ recommendations regarding the use of validated instruments, and regularly confirm personnel qualifications. External quality control of plague diagnostics in anti-plague institutions using encrypted panels containing Y. pestis samples that simulate real biological samples is an effective tool for monitoring laboratory performance, ensuring the quality of laboratory testing, and maintaining the reliability of diagnostic results.

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