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

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.

Perspectiva interdisciplinaria para el abordaje de una enfermedad infecciosa: chagas o tripanosomiasis americana / Interdisciplinary perspective to approach an infectious disease: american trypanosomiasis or chagas disease

La enfermedad de Chagas, producida por elTrypanosomacruziy transmitida por un insecto triatomino, es de grancomplejidad. En el control de esta endemia no puedeconsiderarse la enfermedad como un hecho individualy sólo biológico. Entre sus múltiples componentes debeconsiderarse la relación de los sujetos con el hábitat, losmodos de producción, las condiciones culturales, lasrelaciones sociales y las formas organizativas.Como profesionales del campo de la salud intentamosnuevos enfoques que integran diferentes miradas disciplinaresy modos de intervención distintos, donde “el otro” recuperesu ser sujeto y no esté convocado a desempeñar un merorol de paciente. Posiciones que implican favorecer procesosparticipativos, escuchar a los propios protagonistas (mujerescon Chagas, equipos de salud, referentes comunitarios)recuperar sus peculiares visiones, poner en palabras lo nodicho sobre esta enfermedad silenciosa y silenciada, y develarlo que el Chagas esconde. Constituye una herramientaimportante a la hora de pensar propuestas de trabajo.

Chagas disease, caused by Trypanosoma cruzi and transmitted by a triatomine insectis extremely complicated. When controlling this endemic disease, the disease cannot beconsidered as an individual and merely biological fact. Among its many components therelationship of individuals to the habitat, production modes, cultural conditions, socialrelationships and organizational forms must be considered.As health professionals we present new approaches that integrate different disciplinesand modes of intervention, where “the other” recovers his/her individual being and isnot merely called upon to play a role as a patient. Positions that encourage participativeprocesses involving listening to the protagonists themselves (women with Chagas, healthteams, community references), recovering their unique visions, communicating what isnot said about this silent and hushed up disease, and revealing what Chagas hides areimportant tools when thinking about work proposals.