Comparisons of immunological tests for serodiagnosis of Chagas disease in Bolivian patients
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Abstract. Enzyme linked immunosorbent assay (ELISA) and immunoelectrophoresis (IEP) were evaluated and compared to the classical immunofluorescence (IF) and complement fixation test (CFT) in the immunological diagnosis of Chagas' disease, using 407 sera from Bolivian patients. 72.7 to 79.5% of randomised sera, coming from patients living in endemic areas for Chagas' disease were considered as positive, according to the test limits, previously determined. The techniques could be classified according to their percentage detection as ELISA > IF > CFT > IEP. The quantitative correlations between the tests were excellent (p < 0.001). 92.8% of the sera were positive or negative for the four tests, 6.1% for three tests and 1.1% for only two tests. The agreement between the tests ranged from 94.6 to 99.2%, co-positivity from 95.5 to 100% and co-negativity from 88.5 to 100%. IF gave the best results, and could be considered as the reference test since it was easy and rapid to perform. However to avoid errors or discrepancies between laboratories, two tests, such as IF and CFT, might be associated. ELISA can be used if higher sensitivity is required. IEP showed 1 to 14 precipitation bands in 96% of the sera from infected patients. The precipitation band 5, previously demonstrated as Trypanosoma cruzi specific, was present in 73% of these sera, indicating the interest to use immunoprecipitation test, if more specificity is required for the immunodiagnosis of Chagas' disease.