Geographical origin of chronic Chagas disease patients in Brazil impacts the performance of commercial tests for anti-T. cruzi IgG

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.