Comparison of four serological tests for the diagnosis of Chagas disease in a Colombian endemic area.

The performance of 4 serological tests for the diagnosis of Chagas disease was evaluated in Santander, Colombia, a region still presenting active transmission. Serum samples from 638 individuals were submitted to an enzyme immunoassay test (EIA), using total lysate of a local Trypanosoma cruzi strain and 52.5% were positive (335/638). A subset of this group (94 positive individuals and 90 seronegatives) was randomly selected for further serological confirmation. Three additional tests were used--indirect immunofluorescence (IIF) and 2 distinct enzyme-linked immunosorbent assays using total lysate of the Y strain (EIA BM) and a mixture of 2 recombinant antigens (EIA RA). Seventy-nine patients were seropositive in all tests (84.0%-79/94). The number of positive sera with the IIF, EIA RA and EIA BM was 84/94 (89.4%), 80/94 (85.1%) and 79/94 (84.0%), respectively. In 15 out of the 94 EIA seropositive patients (16.0%), 10 individuals were negative in all 3 tests (10.6%-10/94). One was negative in the EIA BM and positive in the other two tests (1.1%-1/94) and 4 patients were positive, solely, in the IIF assay (4.3%-4/94). Relative to the 90 EIA negative individuals, 89 were confirmed in all other tests (98.9%-89/90). One individual, although seronegative in the IIF, was positive in both confirmatory EIA tests (1.1%-1/90). In addition, 120 blood specimens were submitted to PCR amplification. This group consisted of 79 confirmed seropositive cases, 16 individuals with discordant serological results and 25 validated seronegative individuals. The PCR was able to detect the presence of parasite DNA in 67 out of the 79 seropositive patients (84.8%), in 8 individuals with discordant serology (50.0%) and in only one seronegative individual (4.0%). The results pointed to the necessity for performing more than one serological test, preferentially with antigens from autochthonous strains, to achieve a reliable diagnosis of Chagas disease in Colombia.