[Serological diagnosis of Chagas disease: self-sufficiency and interlaboratory concordance]. / Diagnóstico serológico de la enfermedad de Chagas: autosuficiencia y concordancia interlaboratorios.

American trypanosomiasis (Chagas' disease) is becoming a relatively common condition in North America. Diagnosis at the chronic stage depends on demonstration of specific antibodies in body fluids, since parasitologic or pathologic diagnosis is uncertain at this stage. Therefore, standardization of immunodiagnostic techniques is mandatory, and it depends on antigen quality. Locally prepared antigens and crude extracts obtained from Mexican isolates, -both from infected vector and human cases-were compared using three different immunodiagnostic assays-indirect immunofluorescence, hemagglutination and enzyme linked immunosorbent assay (ELISA)-at two different laboratories from the Instituto Nacional de Cardiología and the Instituto Nacional de Diagnóstico y Referencia Epidemiológicos. Concordance between laboratories reached a significant Kappa value (0.8) and sensitivity, specificity and predictive values of individual diagnostic assays were adequate to use these tests in clinical diagnoses. This is the first attempt to standardize immunodiagnostic techniques in Mexico.

[Detection of antibodies against Trypanosoma cruzi in blood donors]. / Detección de anticuerpos contra Trypanosoma cruzi en donadores de sangre.

American trypanosomiasis is an endemic disease in Mexico. Blood transfusion has been recognized as the second main mechanism of transmission in South American countries. There is no definitive information available for Mexico. We obtained the prevalence of IgG antibodies against Trypanosoma cruzi among 1076 blood donors at the Instituto Nacional de Cardiología "Ignacio Chávez" in Mexico City. We used an antigen freshly prepared from local isolates, and the complete and soluble antigen preparations were analyzed with the Western blot technique using sera previously characterized as reactive. Blood donors' antibodies were studied with DOT-ELISA and Western blot. All donors were asked in regard to place of birth, and blood samples were serologically tested as usual in transfusion practice. The presence of IgG antibodies to T. cruzi, confirmed with a high-specificity test, showed a prevalence of 0.28 per cent. Screening for antibodies to T. cruzi; should be included in the evaluation of blood donors in Mexico.