Comparative evaluation of the Rose Bengal plate test, standard tube agglutination test and complement fixation test for the diagnosis of human brucellosis

In this study, 241 serum samples from individuals exposed to brucellosis were subjected to the Rose Bengal plate test (RBPT); the titre was estimated by standard tube agglutination test (STAT), with positive > or = 80 IU/ml. Randomly selected sera (n = 81) were analysed by complement fixation test (CFT): titre > or = 1:4 was considered positive. Of 241 sera subjected to RBPT and STAT, 177 were negative in both tests; 5 samples tested negative by RBPT but positive by STAT. None was positive by RBPT and negative by STAT. Of 81 sera subjected to CFT, 23 (28.4%) were positive. Both RBPT and CFT found 18 samples positive; 5 samples were positive by CFT and negative by RBPT. Comparison of STAT with CFT showed 13 samples positive by STAT but negative by CFT, and 4 positive by CFT but negative by STAT. The sensitivity and specificity of STAT were 82.6% and 77.6%, respectively, with CFT as gold standard. No test is perfect, and the clinical history coupled with a combination of two or more tests will reduce diagnostic errors.