Evaluation of sensitivity, specificity and cross-reactivity in Bartonella henselae serology.

Laboratory diagnosis of cat-scratch disease (CSD) mainly relies on serological testing for Bartonella henselae antibodies by indirect immunofluorescence (IFA) or enzyme-linked immunoassay (ELISA). In this study the current diagnostic value of seven B. henselae serological tests was evaluated, including both commercial and in-house IFA’s as well as in-house ELISA. Fifty patients with proven CSD, based on the presence of lymphadenopathy, positive PCR and no other diagnosis, were compared to 55 controls initially suspected for CSD but tested negative in PCR and who ultimately received a different diagnosis. Cross-reactivity was tested in serum samples positive for infection with Epstein-Barr virus (n = 141), cytomegalovirus (n = 39), Toxoplasma gondii (n = 20), Streptococcus pyogenes (n = 54), Chlamydophila pneumoniae (n = 14) and Coxiella burnetii (n = 21). Sensitivity was higher in the two IgG tests (88-98%) than in the IgM tests (50-64%). Adding genotype II strains to the IgM IFA did not improve sensitivity and resulted in higher crossreactivity. Specificity was higher in the IFA IgM tests (up to 95-96%) than in the Focus IgG tests (69%). The concurrent use of both IgM and IgG Euroimmun IFA improved sensitivity to 92% with a specificity of 84%. Cross-reactivity in lymph node diseases was 0-5% in the Houston-strain IgM IFA’s, 0-8% in IgG IFA and 5-24% in the IgM ELISA. Cross-reactivity was 0-36% in C. pneumoniae and 13-30% in C. burnetii, depending on the test. The results of this study indicate that the combined use of IgM and IgG IFA’s based on co-cultivation can be useful in serodiagnosis of CSD. 97 Sensitivity, specificity and cross-reactivity in CSD serology