Evaluation of in-house and commercial serological tests for diagnosis of human tularemia.

4 years ago

Evaluation of in-house and commercial serological tests for diagnosis of human tularemia.

Aurélie Hennebique, Dominique J Bicout, Sandrine Boisset, Yvan Caspar, Isabelle Pelloux, Max Maurin, Hadjila Yanes

Tularemia is a zoonosis caused by the bacterium Francisella tularensis Its specific diagnosis remains based on serological methods, while detection of F. tularensis in clinical samples by culture or PCR is rarely obtained. The aim of the present study was to evaluate the performance of the SERION ELISA classic Francisella tularensis IgG and IgM tests (Virion/Serion GmbH Institute, Würzburg, Germany) and the VIRapid® Tularemia immunochromatographic (ICT) test (VIRCELL, Granada, Spain), compared to the in-house microagglutination (MAT) and indirect immunofluorescence (IFA) tests currently used at the French National Reference Centre for Francisella.We evaluated 256 consecutive sera from 208 patients, including 51 confirmed and 23 probable tularemia cases, and 134 control patients not infected with F. tularensis The IFA tests displayed 72.5% sensitivity for IgM (cut-off titer ≥80) and 74.5% for IgG (cut-off titer ≥160), and 99.3% specificity for both IgM and IgG. Using cut-offs advocated by the manufacturer, the Serion ELISAs displayed 88.2% sensitivity for IgM and 86.3% for IgG antibodies, and 94.8% specificity for IgM and 95.5% for IgG. Compared to the MAT and IFA tests, the Serion ELISA tests allowed earlier detection of specific antibodies (1--2 weeks versus 2--3 weeks after the onset of symptoms). The ICT sensitivity and specificity were respectively 90% and 83.6% when considering the cut-off advocated by the manufacturer. In conclusion, the Serion ELISAs are useful as screening tests for tularemia diagnosis, but additional confirmatory tests (such as MAT and IFA) are needed, especially in low-endemic areas.

Publisher URL: http://doi.org/10.1128/JCM.01440-17

DOI: 10.1128/JCM.01440-17