A reliable and specific enzyme-linked immunosorbent assay for the capture of IgM from human chagasic sera using fixed epimastigotes of Trypanosoma cruzi

A rapid, sensitive, specific, and reliable enzyme-linked immunosorbent assa y (ELISA) is proposed for determination of the levels of anti-Trypanosoma c ruzi IgM in acute chagasic sera (ACD). The efficiency of this ELISA as a di agnostic method was compared with that of parasite DNA detection by polymer ase chain reaction (PCR) and that of indirect immunofluorescence (iIF) anti -ir. cruzi IgM detection. We tested whether this ELISA using fixed epimasti gotes (epi) could detect anti-T. cruzi IgM in serum samples from two groups of children with acute Chagas' disease from a hyperendemic area in Bolivia . In a comparison of the ELISA method with other techniques, 95% and 71% of the results correlated with PCR and iIF findings, respectively. At the ser um dilution applied (1:250), rheumatoid factor (RF) did not influence the r esults, and samples from patients carrying leishmaniasis or mixed Leishmani a and T. cruzi infection could also be excluded from ACD. Highly specific a nd reliable results were obtained, a great number of the sera could be test ed in only one assay, and a quantitative index of reactivity (IR) could be calculated without serial titration. Using test samples in triplicate, the method provides a useful tool for the detection of early acute-phase T. cru zi infection in humans.