A comparative study of four serological methods for diagnosis of acute and chronic Chagas' disease in Brazilian patients.

Complement fixation (CF), indirect immunofluorescence (IFAT), latex agglutination (LA) and the enzyme-linked immunosorbent assay (ELISA) were applied to assess the diagnostic value of antibody determination in Brazilian patients with acute or chronic Chagas' disease. Patients with various forms of leishmaniasis and healthy individuals from the endemic region were used as specificity controls. Whereas LA, IFAT and ELISA identified 81% of acutely ill patients, CF had no diagnostic potential in this phase of the disease. In later stages CF showed a sensitivity of 69% as compared to 100% for LA, IFAT and ELISA, irrespective whether patients presented clinically as chronic asymptomatic or chronic symptomatic cases. Cross-reactivity with anti-leishmania antibodies was observed in 23%, 38% and 77% of serum samples in LA, ELISA and IFAT, respectively, but not in CF.