BACKGROUND Chagas disease, caused by Trypanosoma cruzi, affects nearly six million people worldwide. Various serological tests have been developed for its diagnosis. OBJECTIVE Examine the performance of a set of commercial immunological assays in relation to the geographical origin of the patient sample comparing four states of Brazil: Amazonas (AM), Mato Grosso do Sul (MS), Minas Gerais (MG) and Piauí (PI). METHODS Seven immunoassays were employed to detect anti-T. cruzi IgG antibodies in 379 patient samples that had been previously diagnosed using the two-step protocol required by the Brazilian Ministry of Health. FINDINGS A significant variation in the percent reactive was calculated for the samples from AM and MS, while the PI and MG showed a significant variation in the percent non-reactive. The average reactivity index was significantly higher for samples from the states of PI and MG states than AM and MS. MAIN CONCLUSIONS All tests presented a satisfactory performance overall. Yet, variations were observed that were associated to the region of origin of the samples. Our analyses suggest that future evaluations of immunoassays should include a sampling of sera from regions where the test will be applied in addition to the available International Biological Reference Standards.

BACKGROUND Chagas disease, resulting from Trypanosoma cruzi infections, continues to be a health concern mainly in Latin American countries where the parasite is endemic. The laboratory diagnosis of a chronic infection is determined through serological assays for antibodies against T. cruzi and several tests are available that differ in key components, formats and methodologies. To date, no single test meets the criteria of a gold standard. The situation is further complicated by the difficulties associated with performance comparisons between different immunoassays or methodologies executed at different times and geographical areas. OBJECTIVE To improve the diagnosis of Chagas disease, the WHO coordinated the development of two International Biological Reference Standards for antibodies against anti-T. cruzi: NIBSC 09/186 and NIBSC 09/188 that respectively represent geographical regions with the highest prevalence of TcII and TcI lineages of the parasite. METHODS The principle goal of this study was to verify the behavior of these standards when assayed by several commercially available serological tests that employ different methods to capture and detect human anti-T. cruzi antibodies. FINDINGS AND MAIN CONCLUSIONS The results reinforce the recommendation that these standards be considered for performance evaluations of commercialised immunoassays and should be an integral step in the development of new test components or assay paradigms.

Visando a aumentar a precisão do diagnóstico, a Organização Mundial da Saúde recomenda executar dois ou mais testes imunoserológicos para o diagnóstico na fase crônica da doença de Chagas. O objetivo deste trabalho foi fazer uma revisão sistemática rápida sobre o desempenho de técnicas imunoserológicas e métodos moleculares na população em geral. Foram identificados 178 estudos dos quais se incluíram nove. Técnicas de ELISA mostraram a maior sensibilidade (82-98%) e especificidade (96-100%). Métodos rápidos apresentaram valores de sensibilidade e especificidade de 88-93% e 97-100%, respectivamente enquanto que os métodos moleculares (PCR) tinham níveis extremamente variáveis de sensibilidade (22-92%) e especificidade (70-100%). Estes resultados mostram que as técnicas de ELISA possuem sensibilidade e especificidade adequadas. A PCR, bem como os métodos rápidos, mostrou grande variabilidade nos resultados, principalmente devido à heterogeneidade das técnicas e profusão de métodos desenvolvidos de modo in house.

In order to increase diagnostic accuracy, the World Health Organization recommends performing two or more immunoserological tests for the diagnosis of Chagas disease in chronic stage. The aim of this work was to make a rapid systematic review of the performance of immunoserological techniques and molecular methods in the general population. A total of 178 studies were identified, nine ofwhich were included. ELISA techniques showed the highest sensitivity (82-98%) and specificity (96-100%). Rapid methods presented values of sensitivity between 88-93% and 97-100% of specificity, while the molecular methods (PCR) showed highly variable levels of sensitivity (22-92%) and specificity (70-100%). These results indicate that ELISA techniques have adequate sensitivity and specificity. PCR, as well as rapid methods, showed great variability in the results, mainly due to the heterogeneity of the techniques and abundance of “in-house” methods.

Con el objetivo de incrementar la precisión diagnóstica, la Organización Mundial de la Salud recomienda la realización de dos o más pruebas inmunoserológicas para el diagnóstico de la enfermedad de Chagas en etapa crónica. El objetivo de este trabajo fue realizar una revisión sistemática rápida acerca del desempeño de las técnicas inmunoserológicas y métodos moleculares en la población general. Se identificaron 178 estudios de los cuales fueron incluidos nueve. Las técnicas de ELISA mostraron la mayor sensibilidad (82-98%) y especificidad (96-100%). Los métodos rápidos mostraron valores de sensibilidad entre 88-93% y especificidad 97- 100%, mientras que los métodos moleculares (PCR) presentaron niveles muy variables de sensibilidad (22-92%) y especificidad (70-100%). Estos resultados muestran que las técnicas de ELISA cuentan con una sensibilidad y especificidad adecuadas. La PCR, al igual que los métodos rápidos, mostró una gran variabilidad en los resultados, debido principalmente a la heterogeneidad de la técnicas y profusión de métodos elaborados de manera in house.