Sensitivity and Specificity of two rapid tests for the diagnosis of infection by Trypanosoma cruzi in a Colombian population

Objective To evaluate diagnostic precision of two rapid diagnostic tests (RDT's) on patients with chronic Chagas disease. Methodology Prospective study with the following inclusion criteria: subjects older than 3 years, signed informed consent. Exclusion criterion: subjects could not have previously received treatment for infection with T. cruzi. The study population were participants in a screening process undertaken in rural and urban zones of the department Boyaca, Colombia. Two RDT's were performed to all participants: the Chagas Detect Plus InBios (CDP) and the Chagas Stat-Pak (CSP) and as a reference standard the ELISA Chagas III GrupoBios and the Chagas ELISA IgG+IgM I Vircell tests were used. In the case of discordant results between the two ELISA tests, an indirect immunofluorescence was done. Results Three hundred-five (305) subjects were included in the study (38 patients with leishmaniasis), of which 215 tested negative for T cruzi and 90 tested positive according to the reference standard. The sensitivity of the RDT's were 100% (CI 95% 95.9-100), and the specificity of the CDP was 99.1% (CI 95% 96.6-99.8) and for CSP was 100% (CI 95% 98.3-100). The agreement of CDP was 99.5% and for CSP was 100% with Kappa values of (k = 99.1; CI 95% 92.6-99.8%) and (k = 100; CI 95% 94.3-100), respectively. RDT's did not present cross-reactions with samples from patients who were positive for leishmaniasis. Conclusions The findings demonstrate excellent results from the RDT's in terms of validity, safety, and reproducibility. The results obtained provide evidence for the recommendation for using these tests in a Colombian epidemiological context principally in endemic areas in which laboratory installations necessary to perform conventional tests are not available, or they are scarce and to help in diagnosing chronic Chagas disease in order to provide access to treatment as soon as possible. Author's summary Chagas is a disease caused by the parasite Trypanosoma cruzi, and is one of the most important public health concerns affecting the population of Latin America. This disease presents an acute phase that generally goes undiagnosed and a chronic phase with cardiac manifests principally, is diagnosed through serological tests that are not available in the majority of regions endemic for Chagas disease (CD), the results may take weeks to be returned due to logistical and operational reasons that comprise the main obstacles in initiating treatment of the disease. In the present article, quality indices of two RDT's were evaluated during a field study in the department of Boyaca Colombia, these tests are easy to administer, require only minimal quantities of sample, provide rapid results and do not require electrical equipment or refrigeration. The sensitivity of the two RDT's was 100% and the specificity of CDP was 99.1% and for CSP was 100% according to reference tests. The results obtained support the recommendation of using RDT's in order to help diagnose chronic Chagas disease and thus to improve access to treatment for the populations studied as soon as possible.

Automated summary

The study evaluated the diagnostic precision of two rapid diagnostic tests (RDT's) on patients with chronic Chagas disease. The RDT's showed high sensitivity and specificity, making them suitable for diagnosing chronic Chagas disease in Colombia and improving access to treatment.