Comparison of the 2-mercaptoethanol and dithiothreitol tests for determining Brucella immunoglobulin G agglutinating antibody in bovine serum.

The dithiothreitol test was evaluated as a substitute for the 2-mercaptoethanol test for determining Brucella immunoglobulin G agglutinating antibody in bovine serum. The tests were compared on 207 card-positive sera that showed a standard tube-agglutination titer of incomplete 1:50 or higher. The tests agreed within one dilution with 182 of the 207 sera tested for an 87.9% rate of agreement. When titers were not the same, those obtained with the dithiothreitol test were more frequently lower than higher than those obtained with the 2-mercaptoethanol test. Sixteen sera that showed a titer with the 2-mercaptoethanol test were negative with the dithiothreitol test and two that showed a titer with the dithiothreitol test were negative with the 2-mercaptoethanol test. Results suggest that the dithiothreitol test is not a reliable substitute for the 2-mercaptoethanol test to detect immunoglobulin G agglutinating antibody in bovine serum.