Real-life assessment of the VirClia® IgG chemiluminescence test for the diagnosis of Bartonella henselae infection

Serology remains the first-line diagnostic method for Bartonella henselae infection. Indirect immunofluorescence assay (IFA) is considered the reference serological assay to detect anti-B. henselae antibodies. However, IFA has the drawbacks associated with manual techniques. Thus, the automated VirClia® Lotus analyser (VLA) was presented as an easy-to-use solution for B. henselae serology. The aim of our study was to evaluate the clinical and analytical performance of the VLA in comparison with a commercial IFA on a population that was representative of the various forms of bartonellosis. This retrospective study included 340 serum samples (one sample per patient). B. henselae infection was diagnosed in 65 patients (20 %): 77 % of patients had regional lymphadenopathy and 17 % had disseminated infection. At the manufacturer's recommended cut-off (0.9), 223 samples had positive or equivocal IgG results by the VLA, and 117 samples were negative. Using IgG IFA as a reference, the sensitivity for IgG VLA reached 87.9 % but the specificity was 46.8 %. As regards clinical performance, the sensitivity for IgG VLA was 92.3 % but the specificity fell to 42.1 %. In comparison, IgG IFA had a sensitivity of 95.4 % and a specificity of 80.5 %. To address the insufficient specificity of IgG VLA, while maintaining optimal sensitivity and the advantages of automated screening, we propose combining this VLA screening with an IFA confirmation test for any serum with an index ≥ 0.9. This two-tiered serological strategy showed a diagnostic sensitivity of 87.7 % and a specificity of 84.0.