Diagnostic value of the indirect immunofluorescence assay in cat scratch disease with Bartonella henselae and Afipia felis antigens

Serum samples from 35 cat scratch disease (CSD) patients, 180 control patients (123 without lymph node enlargement and 57 with lymph node enlargement not evoking CSD), and 102 nonpatient subjects (35 with cat contact and 67 without cat contact) were tested by semiquantitative indirect immunofluorescence assay for the presence of antibodies directed to Afipia felis (ATCC 53690T) or Bartonella henselae (ATCC 49882T). The CSD group had statistically higher antibody titers against B. henselae than the control groups (P < 10(-5)), whereas no difference in A. felis antibody titers was evidenced among all groups tested. Among the 317 serum samples studied, the three with high A. felis antibody titers ( > or = 64) also had high antibody titers against other alpha-2 proteobacteria. The value of the indirect immunofluorescence assay with B. henselae antigen for the diagnosis of CSD was as follows: for a cutoff of 32, sensitivity was 0.80, specificity was 0.85, and the likelihood ratio was 5.1; for a cutoff of 64, the likelihood ratio was 12.1. In summary, in France, CSD is associated with high antibody titers against B. henselae, as previously described in the United States. However, the causes for B. henselae seronegativity in CSD patients and those for high antibody titers outside the typical nosological frame of CSD still have to be identified.