The direct agglutination test for chronic Chagas's disease. The effect of pre-treatment of test samples with 2-mercaptoethanol.

The relative sensitivity and relative specificity of the direct agglutination (DA) test for the diagnosis of human Trypanosoma cruzi infection were studied in human serum samples, with and without previous treatment with 2-mercaptoethanol (2-ME), which were obtained from different areas of Brazil. Results obtained with these tests were related to those obtained with the indirect immunofluorescence (IIF) and indirect haemagglutination (IHA) tests. The DA test results from the sample not previously treated with 2-ME did not agree with those from the IIF and IHA tests. On the other hand, the DA test results from the sample previously treated with 2-ME agreed significantly (99.22%) with those from the IIF and IHA tests.