Comparability and reliability of ELISA, immunofluorescence, and indirect hemagglutination assays for Trypanosoma cruzi and Trypanosoma rangeli.

Serum samples and filter paper spot samples from 48 adults were assayed in three laboratories for Trypanosoma cruzi and Trypanosoma rangeli by ELISA, immunofluorescence (IF), and indirect hemagglutination (HA) in a controlled, blind experiment. IF (serum samples) attained higher levels of comparability necessary for validity than did ELISA (serum samples) in these laboratories. ELISA was inferior to IF and HA (spot samples) in testing for T. cruzi. ELISA was not reliable (intrasubject r = .51) and was not in agreement between two laboratories (kappa = .09). The experiment indicates that ELISA is not the best choice of assay for T. cruzi in epidemiologic surveys. Assays for T. rangeli by ELISA and IF lacked comparability to the extent that those two techniques could not be considered useful for T. rangeli.