DETECTION OF ANTIBODIES TO BARTONELLA-HENSELAE IN CLINICALLY DIAGNOSED CAT-SCRATCH-DISEASE

Objective: To determine the usefulness of an indirect immunofluorescen ce antibody test for antibodies to Bartonella henselae in diagnosing c at scratch disease (CSD). Design and setting: Retrospective case surve y of 354 patients whose sera were tested for antibodies to B. henselae at Royal Perth Hospital, Perth, and the institute of Clinical Patholo gy and Medical Research, Sydney, in 1994; and measurement of the backg round prevalence of antibodies to B. henselae. Main outcome measures: Prevalence of antibodies to B. henselae; odds of a positive titre (gre ater than or equal to 64) in patients with and without specific risk f actors for CSD and clinical features of the disease; prevalence of ant ibodies to a. henselae in randomly selected blood donors. Results: Dem ographic, clinical and cat contact data were available for 303 patient s. Sixty-four (21.1%) had a positive titre, as did 53 of 98 (54%) pati ents with a history of cat contact and lymphadenopathy. This proportio n increased to 62% (38 of 61 patients) in patients with a history of c at scratch or bite and to 90.3% (28 of 31) in those with cat contact, lymphadenopathy and histological evidence of granulomatous lymphadenit is. Patients who developed lymphadenopathy after cat contact were sign ificantly more likely to have a positive titre than those without this history (odds ratio [OR], 20.8; 95% confidence interval [95% CI], 9.6 -46; P<0.0001). Inclusion of a history of a cat scratch or bite signif icantly raised the odds of being seropositive (OR, 13.7; 95% CI, 6.8-2 8.1; P<0.0001), and the presence of granulomas on lymph node biopsy fu rther increased the odds (OR, 124.4; 95% CI, 19.4-1073; P<0.0001). The prevalence of antibodies to B. henselae in random blood donors in New South Wales was about 5% (five of 102 sera samples). Conclusions: The immunofluorescence antibody test for B. henselae can be expected to b e positive in just over half the patients with clinically suspected CS D, and it has a positive predictive value of 83%. In a significant num ber of cases the diagnosis cannot be made on the basis of the results of immunofluorescence antibody testing alone and further investigation s, including lymph node biopsy, may be required.