Chagas' disease screening in blood bank employing enzyme immunoassay

Because of the high prevalence of Trypanosoma cruzi infection in Latin America, antibody screening in blood banks is mandatory in this area. This screening may also become a concern in the U.S.A. considering the high frequency of Latin American donors. The tests usually employed (indirect hemagglutination, direct agglutination, immunofluorescence and latex agglutination assays) involve subjective interpretation of results and do not fit the automated procedures requirements of large laboratories. Thus, an enzyme immunoassay was developed using a mixture of antigens purified from the membrane and the cytoplasm of the parasite. Serum of plasma could be used as sample, in a procedure involving 90 min total incubation time and 2 washing steps. Results could be interpreted either spectrophotometrically or by the naked eye. The method was used to test 661 samples from patients undergoing different stages of Chagas' disease, 120 patients suffering other parasitosis and 880 normal subjects. Results were compared with those obtained with the methods mentioned above. The proposed test showed better reproducibility, specificity and sensitivity than those of reference methods, plus an objective interpretation of results and suitability to automation.