Evaluation of the card test for diagnosis of human brucellosis.

The relative efficacy of the card test in the diagnosis of human brucellosis was evaluated by comparison with four other tests: the standard tube agglutination test, centrifugation agglutination test, 2-mercaptoethanol degradation technique, and 2-mercaptoethanol centrifugation agglutination test. A total of 1,701 serum specimens from persons with various degrees of potential exposure to brucella organisms or cross-reactive antigens were used in this study. In comparison with standard tube agglutination results, the card test had a sensitivity of 95.3% and a specificity of 84.1%. The card-test antigen was nonreactive with serum specimens from tularemia patients and cholera vaccinees. Our data indicated that this test measures both immunoglobulin G and immunoglobulin M agglutinins. The value of the card test in the presumptive serological diagnosis of clinical brucellosis in humans appears to be low; however, the card test may be of value in serological surveys to delineate high-risk populations.