Comparative evaluation of immunoassays to improve access to diagnosis for Chagas disease in Colombia

Abstract

Chagas disease affects over six million people, but less than 1% are diagnosed and treated. Complicated diagnostic processes are a major barrier. Colombia's previous diagnostic algorithm, using inhouse tests, was difficult to scale up, creating significant access barriers for patients. A new algorithm using commercially manufactured immunoassays would potentially improve access, but these tests' performance in Colombian patients with Chagas disease is not well known. Methods: We assessed seven commercially available assays. Samples (n = 501), 93.8% originating from Colombia, were characterized as positive or negative based on standard procedure at the National Reference Laboratory. Performance characteristics were calculated for individual assays and hypothetical test pairings, then compared to the existing algorithm. Results: Five of seven assays exhibited sensitivity >98% while six showed specificity >97%. A total antigen ELISA paired with a recombinant assay provided similar performance to the current diagnostic process. Six of six assays tested proved capable of detecting different Trypanosoma cruzi genetic lineages. Conclusions: The study indicated that several commercial assays accurately detect T. cruzi infection in Colombian patients. A simplified testing process with two commercial assays could perform comparably to the previous process, reducing cost and accessibility barriers and facilitating national scale-up.

Prevalence of Trypanosoma cruzi infection in active military population of The Colombian National Army gathered in five departments

“…Chagas disease has a complexity of diagnostic process, which is hampered by the lack of a gold standard, availability of multiple types of assays with varying sensitivity and specificity, and the sheer difficulty of detecting the parasite in the chronic phase leaves the diagnosis to be only conducted for this phase through out detection on antibodies [32]. Moreover, another of the common problems in serological diagnosis of Chagas disease is the cross-reactions that result from infections with another type of trypanosomatids [33–35].…”

“…Additionally, for the recognition of vectors, we teach dissected images and triatomines to the interviewees, it is possible that the group of participants who said they had contact with triatomines during the presentation of the service, confused these vectors with other reduced predators and phytophagous who inhabits in colombian jungles. Finally, another important limitation of our study is the impossibility of evaluating the impact of cross-reactions or co-infection with Trypanosoma rangeli , another trypanosomatide that circulates in Colombia due to the absence of reference serum for this parasite [32, 41]…”

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

“…The reference diagnostic strategy utilized in the present study is based on conventional serological tests suggested by the National Parasitology Reference Laboratory of the National Health Institute (Instito Nacional de Salud, or INS) of Colombia [20], and is routinely used in the CD monitoring program of the LDSP. All samples were analyzed using the ELISA Chagas III GrupoBios tests [informed sensitivity, 100%; specificity, 100%] [29] and with the Chagas ELISA IgG+IgM I Vircell tests [informed sensitivity, 100%; specificity, 98%] [30,31]. In cases in which discordant results were found between the two ELISA tests, an IIF test was done [32], which uses epimastigotes of the Colombian T. cruzi strains DTU and TcI as antigens, when the results of this technique were positive, case was considered to be confirmed.…”