Enzyme immunoassay (EIA) for the diagnosis of cat scratch disease (CSD)

Bartonella henseiae (Bh) is the principal agent of CSD; Afipia felis (Af) is an occasional cause, while B. quintana (Bq) is not. Utility of serologic confirmation of CSD by EIA using n-lauroylsarcosine-insoluble antigens from Bh, Bq, and Af was evaluated in 3 groups: Definite CSD (DCSD; corroborated by culture, PCR or skin test; n=50), clinical CSD (CCSD; clinical syndrome without such corroboration; n=43), and uninfected contols (n=60). Assay results (% positive): Bh-reactive Bq-reactive Af-reactive IgG IgM IgG IgM IgG IgM DCSD 78.0 68.0 38.0 20.0 10.0 10.0 CCSD 53.5 48.8 20.9 9.3 25.6 9.3 CONTROLS 1.7 0.0 3.3 3.3 1.7 3.3 Bh EIA results were highly specific, 98.3 and 100% for IgG and IgM, respectively. When a positive IgG and/or IgM result was considered diagnostic, EIA sensitivity was 96%. Most antibody (Ab) reactions to Bq likely represented cross-reaction with Bh, as they were lower in magnitude than concurrent reactions to Bh. No association was found between Bh EIA IgG status and anti-CHIamydia pneumoniae IgG (tested by microimmunofluorescence). However, Abs reactive with Af were present in a number of CCSD cases in the absence of Abs to Bh, suggesting Af as a potential alternative etiology of the lymphadenopathy in those. Where Abs reactive to both Bh and Af were detected, coinfection could not be readily distinguished from cross-reaction. In conclusion, the combination of Bh IgG and IgM is an excellent tool in the diagnosis of CSD.