lmmunodiagnosis of Chagas' disease by ELlSA

Abstract

Demonstration of the infectious agent is the gold standard in parasitic infections but this is not always feasible.Thus diagnosis is confirmed through Trypanosoma cruziantibody detection (in the case of Chagas'disease) by using serological assays. In this study the enzyme immunoassay (ELISA) for the diagnosis of Trypanosoma cruz; infection was standardised and assessed. 595 serum samples taken from people coming from the endemic area of Guateque, Boyaca, were tested against T. cruziepimastigotes from the IRHOlCOl69lGuateque Colombian strain, using both the immunofluorescent antibody test (IFAT) and the ELlSA test. Analysis of the ELlSA test's validity was done through estimation of the area under the receptor-operator curve (ROC). The optimum conditions for the ELlSA test were an antigen concentration of 0.75 ygrlml and sample dilution of 1:1000. The assay's sensitivity for cut-off points of 0.2, 0.3, 0.4 and 0.5 was 0.99, 0.99, 0.98 and 0.93 and its specificity for the same cut-off points was 0.94, 0.96, 0.98 and 0.98.The ELlSA test is a valid and useful test, not only because of its sensitivity and specificity but also because the estimation of the area under the receptor-operator curve (ROC) was 0.9952, this being very close to the ideal. The ELlSA test is better than the IFAT test for detection of Trypanosoma cruzi infection antibodies and could be used in seroepidemiological sur'veys in areas of moderate to high prevalence.