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 ANTIBODIESTO TRYPANOSOMA-CRUZI

Background: Chagas' disease or American trypanosomiasis, caused by inf ection with Trypanosoma cruzi, is a significant health problem in Lati n America. In the United States, transfusions of T: cruzi-contaminated blood from Latin American immigrants may represent the major source o f Chagas' disease. Study Design and Methods: A new enzyme immunoassay (EIA) for the detection of antibody to T:cruzi was evaluated in the se ra of blood donors from the southwestern and western regions of the Un ited 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 a nd by radioimmunoprecipitation assay. Results: Fourteen of the 13,309 donor samples (0.105%) were confirmed as being positive for antibody t o T:cruzi. The Chagas antibody EIA showed improved sensitivity over th e Chagas IgG enzyme-linked immunosorbent assay and two indirect hemagg lutination 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, in direct hemagglutination assay, and immunofluorescence assays). Conclus ion: This Chagas antibody EIA meets the need for accurate and rapid id entification of seroreactive samples in low-prevalence or endemic popu lations.