Diagnostic accuracy of the TR Chagas Bio-Manguinhos rapid test in the municipality of Canguçu, Rio Grande do Sul, a historically endemic area for Chagas disease in Southern Brazil: a prospective study.

Chagas disease (CD), a neglected tropical disease caused by the protozoan Trypanosoma cruzi, remains underdiagnosed across endemic Latin America, in part because access to laboratory-based serological assays is restricted in primary healthcare settings. Rapid diagnostic tests (RDTs) have been advanced as tools to expand serological screening for Trypanosoma cruzi infection, but their performance varies across epidemiological contexts. We evaluated the diagnostic accuracy of the TR (Teste Rápido, Portuguese for "rapid test") Chagas Bio-Manguinhos rapid test in a historically endemic municipality of southern Brazil. A prospective, cross-sectional diagnostic accuracy study was conducted with 333 serum samples consecutively collected from adults attending public and private healthcare facilities in Canguçu, Rio Grande do Sul, between December 2022 and May 2024. The reference serological classification was established using a stepwise algorithm based on two enzyme-linked immunosorbent assays (ELISAs) with different antigenic compositions, with discordant results resolved by a third confirmatory ELISA. Sensitivity, specificity, accuracy, predictive values, likelihood ratios, the diagnostic odds ratio (DOR), and Cohen's kappa were estimated with Wilson score 95 % confidence intervals (CIs). Sixty samples (18.0 %) were classified as T. cruzi-positive. The TR Chagas Bio-Manguinhos showed a sensitivity of 98.3 % (95 % CI 91.1-99.7), specificity of 97.4 % (95 % CI 94.8-98.8), overall accuracy of 97.6 % (95 % CI 95.3-98.8), and almost perfect agreement with the reference algorithm (κ = 0.922; 95 % CI 0.868-0.975). Sensitivity remained high across sex and age strata, and predictive values were strongly prevalence-dependent. These findings provide independent regional evidence supporting the use of the TR Chagas Bio-Manguinhos as a frontline screening tool in southern Brazil, complementing recent multicenter evidence from the Southern Cone.