Comparative performance of the enzyme-linked immunosorbent assay (ELISA) and conventional assays in the diagnosis of bovine brucellosis in Argentina.

The FAO/IAEA enzyme-linked immunosorbent assay (ELISA) kit for the diagnosis of bovine brucellosis was compared in Argentina with two screening tests, the Rose Bengal (RB) and the buffered plate antigen (BPA) agglutination tests and with two confirmatory tests, the 2-mercaptoethanol (2-ME) agglutination and the complement fixation (CF) tests. In the testing of Brucella abortus Strain 19 (S19) vaccinated cattle from Brucella-free dairy herds, the diagnostic specificity estimate of the ELISA (99.7%) was shown to be comparable to the RB (99.7%), 2-ME (99.8%) and CF (99.9%) and greater than the BPA (90.6%). In the testing of S19 vaccinated cattle from infected herds, the sensitivity estimates of the BPA (99.5%, 99.6% and 98.6% respectively) relative to CF,2-ME and ELISA positive reactors were comparable and high. The relative sensitivity estimates of the RB (86.3%, 81.4% and 79.1%) in the same comparison were disparate and lower. The ELISA demonstrated the highest relative sensitivity estimates (97.1% and 95.2% respectively) in a three-way comparison between ELISA, CF and 2-ME positive reactors from these herds. Relative to BPA positive reactors from the same infected herds, the sensitivity estimate of the ELISA (57.0%) was comparable to the 2-ME (56.2%) and higher than the CF (51.8%). These results would suggest that the overall diagnostic specificity and sensitivity of the ELISA test is comparable, if not superior, to the tests used to confirm BPA positive reactor status.