SEROLOGICAL DIAGNOSIS OF CHAGAS-DISEASE - A POTENTIAL CONFIRMATORY ASSAY USING PRESERVED PROTEIN ANTIGENS OF TRYPANOSOMA-CRUZI

The diagnosis of Chagas' disease relies mostly on data provided by imm unologic tests, but inconclusive results often require elucidation, es pecially in blood banks, When six different types of Trypanosoma cruzi epimastigote antigens were studied by an immunoblotting assay (IBA), a preserved protein antigen (Ag PP) was found to present the most inte resting immunochemical features because of its high reactivity with an ti-T. cruzi antibodies, Thus, the IBA with Ag PP (PP IBA) was assessed with panels of coded and noncoded serum samples prepared in different laboratories, including the Brazilian Reference Laboratory for Chagas ' Disease, It was found that serum samples from patients proved (clini cally, eletrocardiographically, serologically, and epidemiologically) to have Chagas' disease consistently recognized 12 bands (140, 100, 85 , 78, 59, 57, 46, 35, 27, 23, 20, and 18 kDa) of Ag PP, In contrast, s era from nonchagasic patients, including patients with mucocutaneous l eishmaniasis, were negative or reacted weakly, and one serum sample di d not have more than five different bands. These bands were 78, 57, 46 , 35, 27, 23, 20, or 18 kDa, A criterion was adopted to interpret the results obtained in the PP IBA, The criterion considered positive a se rum sample recognizing all 12 bands and considered negative a serum sa mple that did not recognize any of the bands except the eight nonspeci fic hands mentioned above, The PP IBA indicated maximum sensitivity an d specificity as well as high positive and negative predictive values, The data demonstrate that the PP IBA discriminates chagasic from nonc hagasic infections and seems to be applicable as a confirmatory assay for elucidating inconclusive results obtained by standard serology.