Pitfalls and fallacies of cat scratch disease serology: Evaluation of Bartonella henselae-based indirect fluorescence assay and enzyme-linked immunoassay

The diagnostic value of the detection of immunoglobulin G (IgG) and IgM by Bartonella henselae-based indirect fluorescence assay (IFA) and enzyme-linked immunoassay (EIA) for the diagnosis of cat scratch disease (CSD) was evaluated, The IFA was performed either with B. henselae that was cocultivated for a few hours with Vero cells or,vith noncocultivated B. henselae as the antigen, Additionally, the performance of a Bartonella PCR hybridization assay based on the 16S rRNA gene was determined and compared,vith those of the serologic assays. The study group consisted of 45 patients suspected of suffering from CSD by fulfilling one or more of the classical criteria. The specificities of the immunoassays were set at greater than or equal to 95% by analysis of sera from 60 healthy blood donors. It is shown that the sensitivities of the IgG assays are very low (40.9% for the IFA with noncocultivated B, henselae as antigen) and that those of the IgM assays are higher (71.4% for the EIA) for patients who fulfilled two or more criteria for CSD, The IgM EIA showed the highest sensitivity: 71.4% in patients with two or more criteria for CSD and 80.6% for patients with a positive Bartonella PCR result. The results indicate that the specificities of both IFA and ELA IgG serologies and the sensitivity of the IFA IgM serology need to be improved. The PCR hybridization assay showed a sensitivity of 86.4% for patients who fulfilled two or more criteria for CSD and 100% for seven patients who fulfilled three or more criteria. The kinetics of IgG and IgM antibody production were studied in 18 patients with CSD on the basis of a positive B, henselae IFA IgM serology. The results indicate that there is no standard course of anti-B. henselae IgG and IgM production in patients with CSD, because some patients produced high levels of both IgG and IgM, others produced only high levels of IgM, and a few patients produced only low levels of antibodies.