DIAGNOSIS OF BABESIOSIS - EVALUATION OF A SEROLOGIC TEST FOR THE DETECTION OF BABESIA-MICROTI ANTIBODY

To assess the possibility of standardization of a commonly used indire ct immunofluorescent antibody (IFA) test for detection of Babesia micr oti antibody in human sera, the results from four reference laboratori es were compared. Patients with babesiosis from southern New England ( n = 25) and subjects with no history of babesiosis from southern New E ngland (n = 55) and Iceland (n = 50) were enrolled in the study. Anti- Babesia antibody titers were determined in a blinded fashion by IFA te st. The range of test results in the four laboratories was 88%-96% sen sitivity, 90%-100% specificity, 69%-100% positive predictive value, an d 96%-99% negative predictive value. interlaboratory and intralaborato ry concordance ranged from 84% to 85% and 94% to 100%, respectively. T his B, microti IFA procedure is a sensitive, specific, and reproducibl e method for diagnosing babesiosis and is suitable for use as a standa rd in laboratories testing human sera for B. microti antibody.