Rapid diagnostic tests duo as alternative to conventional serological assays for conclusive Chagas disease diagnosis

Abstract

Chagas disease is caused by the parasite Trypanosoma cruzi. It affects several million people, mainly in Latin America, and severe cardiac and/or digestive complications occur in ~30% of the chronically infected patients. Disease acute stage is mostly asymptomatic and infection goes undiagnosed. In the chronic phase direct parasite detection is hampered due to its concealed presence and diagnosis is achieved by serological methods, like ELISA or indirect hemagglutination assays. Agreement in at least two tests must be obtained due to parasite wide antigenic variability. These techniques require equipped labs and trained personnel and are not available in distant regions. As a result, many infected people often remain undiagnosed until it is too late, as the two available chemotherapies show diminished efficacy in the advanced chronic stage. Easy-to-use rapid diagnostic tests have been developed to be implemented in remote areas as an alternative to conventional tests. They do not need electricity, nor cold chain, they can return results within an hour and some even work with whole blood as sample, like Chagas Stat-Pak (ChemBio Inc.) and Chagas Detect Plus (InBIOS Inc.). Nonetheless, in order to qualify a rapidly diagnosed positive patient for treatment, conventional serological confirmation is obligatory, which might risk its start. In this study two rapid tests based on distinct antigen sets were used in parallel as a way to obtain a fast and conclusive Chagas disease diagnosis using whole blood samples. Chagas Stat-Pak and Chagas Detect Plus were validated by comparison with three conventional tests yielding 100% sensitivity and 99.3% specificity over 342 patients seeking Chagas disease diagnosis in a reference centre in Sucre (Bolivia). Combined used of RDTs in distant regions could substitute laborious conventional serology, allowing immediate treatment and favouring better adhesion to it.

Chagas disease in the Bolivian Chaco: Persistent transmission indicated by childhood seroscreening study

“…This, coupled with the high FOI estimate, demonstrates significant recent vector transmission. Although the specificity of the CDP (91.9%) in this study was lower than that reported in previous analyses, screening in this rural village was greatly facilitated by the use of this rapid test (Eguez et al, 2017;Shah et al, 2014). Pairing a highly sensitive rapid test with a more specific confirmatory test allows efficient screening, even in a challenging community setting.…”

Complementary Paths to Chagas Disease Elimination: The Impact of Combining Vector Control With Etiological Treatment

“…Promising progress toward the development of better diagnostics has been reported in recent years, with validation of rapid diagnostic tests (RDTs) showing similar performance to classical serological tests. RDTs have the additional benefit of requiring less trained personnel and laboratory infrastructure [ 23 ]. Table 1 summarizes potential strategies for improving the PPC.…”

Response to `letter to the editor: ‘Strategies to enhance access to diagnosis and treatment for Chagas disease patients in Latin America’´

“…Regarding the first, we deeply agree with the concerns of the letter authors on the reduced access to Polymerase Chain Reaction (PCR) and conventional serology (ELISA) tests for the diagnosis of Chagas disease in many areas where the disease is highly endemic and only poorly equipped laboratories are available. In fact, our team at ISGlobal is working at present in a research line which aims to show that the use of alternative diagnostic methodologies, easier to use in those regions, can indeed substitute conventional diagnostics [4,5]. This is, in our opinion, the most urgent necessity in relation to Chagas disease diagnostics at the moment: validation and implementation of rapid diagnostic tests (RDTs) to diagnose chronic infections, and easy-to-use molecular tools such as loop mediated isothermal amplification (LAMP) to early detect congenital transmission events [6].…”