DETECTION OF ANTIBODIES TO TRYPANOSOMA-CRUZI AMONG BLOOD-DONORS IN THE SOUTHWESTERN AND WESTERN UNITED-STATES .1. EVALUATION OF THE SENSITIVITY AND SPECIFICITY OF AN ENZYME-IMMUNOASSAY FOR DETECTING ANTIBODIES TO TRYPANOSOMA-CRUZI

Background: Chagas' disease or American trypanosomiasis, caused by infection with Trypanosoma cruzi, is a significant health problem in Latin America. In the United States, transfusions of T: cruzi-contaminated blood from Latin American immigrants may represent the major source of Chagas' disease. Study Design and Methods: A new enzyme immunoassay (EIA) for the detection of antibody to T:cruzi was evaluated in the sera of blood donors from the southwestern and western regions of the United States. Serum samples had been screened and were negative for all tests required. Specimens that were repeatedly reactive in the Chagas antibody EIA were analyzed for seroreactivity by a confirmatory EIA and by radioimmunoprecipitation assay. Results: Fourteen of the 13,309 donor samples (0.105%) were confirmed as being positive for antibody to T:cruzi. The Chagas antibody EIA showed improved sensitivity over the Chagas IgG enzyme-linked immunosorbent assay and two indirect hemagglutination assays. The Chagas antibody EIA had a specificity of 99.98 percent with negative samples. The sensitivity of the Chagas antibody EIA was 100 percent (80/80) in xenodiagnosed specimens and 100 percent (50/50) in specimens positive by consensus (i.e., reactive in EIA, indirect hemagglutination assay, and immunofluorescence assays). Conclusion: This Chagas antibody EIA meets the need for accurate and rapid identification of seroreactive samples in low-prevalence or endemic populations.