Diagnostic reliability of an immunochromatographic test for Chagas disease screening at a primary health care centre in a rural endemic area

Abstract

Many patients with Chagas disease live in remote communities that lack both equipment and trained personnel to perform a diagnosis by conventional serology (CS). Thus, reliable tests suitable for use under difficult conditions are required. In this study, we evaluated the ability of personnel with and without laboratory skills to perform immunochromatographic (IC) tests to detect Chagas disease at a primary health care centre (PHCC). We examined whole blood samples from 241 patients and serum samples from 238 patients. Then, we calculated the percentage of overall agreement (POA) between the two groups of operators for the sensitivity (S), specificity (Sp) and positive (PPV) and negative (NPV) predictive values of IC tests compared to CS tests. We also evaluated the level of agreement between ELISAs and indirect haemagglutination (IHA) tests. The readings of the IC test results showed 100% agreement (POA = 1). The IC test on whole blood showed the following values: S = 87.3%; Sp = 98.8%; PPV = 96.9% and NPV = 95.9%. Additionally, the IC test on serum displayed the following results: S = 95.7%; Sp = 100%; PPV = 100% and NPV = 98.2%. Using whole blood, the agreement with ELISA was 96.3% and the agreement with IHA was 94.1%. Using serum, the agreement with ELISA was 97.8% and the agreement with IHA was 96.6%. The IC test performance with serum samples was excellent and demonstrated its usefulness in a PHCC with minimal equipment. If the IC test S value and NPV with whole blood are improved, then this test could also be used in areas lacking laboratories or specialised personnel.

Development of a New Lateral Flow Assay Based on IBMP-8.1 and IBMP-8.4 Chimeric Antigens to Diagnose Chagas Disease

“…Similar results have already been found for other RDTs employing multiepitope fusion peptides, such as Trypanosoma Detect, Simple Chagas WB, and Chagas Detect Plus, as well as recombinant or native antigen matrices, namely, Chagas Stat-Pak, WL Check Chagas, Chagas Quick Test, ICT-Operon, and PATH-Lemos Rapid Test [26][27][28][29][30][31][32][33][34][35][36][37]. In fact, other studies employing samples from immigrants living in nonendemic settings or from individuals from endemic Latin American countries reported sensitivity between 88% and 100%, while specificity ranged from 94% to 100% [26][27][28][29][30][31][32][33][34][35][36][37]. In regard to blood donors and T. cruzi-positive individuals from Central America, RDT upheld a sensitivity of 99.6% and a specificity reaching 100% [34].…”

Simultaneous use of two rapid diagnostic tests for the diagnosis of Chagas disease

“…Sensitivity and specificity values of these RDTs are similar to those reported by Sa´nchez-Camargo et al, who evaluated 11 tests individually, and to values reported in other studies using serum samples, but better than values reported using whole blood. [3][4][5][6][7] An excellent correlation was observed between the results of both RDTs, as shown by the high percentage of overall agreement, the Chamberlain's percent positive agreement and the k statistic, with the latter value minimising the influence of agreements due to chance.…”

“…The low sensitivity values obtained with RDT by different authors suggest that they are useful only if used in parallel with a CS test, rendering them less useful in the field. [3][4][5][6][7][8] This low sensitivity is observed mainly when a whole blood sample is used, with test performance being improved when applied to serum samples. Diagnostic sensitivity can be enhanced by performing tests simultaneously on a single sample; however, to date, this option has not been assayed with RDT for CD.…”

Rapid immunochromatographic tests for the diagnosis of chronic Chagas disease in at-risk populations: A systematic review and meta-analysis

“…Four studies were conducted in non-endemic areas (namely, Spain, Switzerland, and Italy)[12,14,15,20]; all studies conducted in LA were carried out in Bolivia, but one that was conducted in Argentina[13]. A couple of studies were conducted in a cohort of children while the others included either adults or individuals of all ages.…”