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 Ig M by Bartonella henselae-based indirect fluorescence assay (IFA) and e nzyme-linked immunoassay (EIA) for the diagnosis of cat scratch diseas e (CSD) was evaluated, The IFA was performed either with B. henselae t hat was cocultivated for a few hours with Vero cells or,vith noncocult ivated B. henselae as the antigen, Additionally, the performance of a Bartonella PCR hybridization assay based on the 16S rRNA gene was dete rmined and compared,vith those of the serologic assays. The study grou p consisted of 45 patients suspected of suffering from CSD by fulfilli ng one or more of the classical criteria. The specificities of the imm unoassays 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 t he 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 t wo or more criteria for CSD and 80.6% for patients with a positive Bar tonella PCR result. The results indicate that the specificities of bot h IFA and ELA IgG serologies and the sensitivity of the IFA IgM serolo gy need to be improved. The PCR hybridization assay showed a sensitivi ty of 86.4% for patients who fulfilled two or more criteria for CSD an d 100% for seven patients who fulfilled three or more criteria. The ki netics 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 pro duced high levels of both IgG and IgM, others produced only high level s of IgM, and a few patients produced only low levels of antibodies.