JCM Accepts, published online ahead of print on 9 April 2008

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J. Clin. Microbiol. doi:10.1128/JCM.02303-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Field evaluation of a rapid immunochromatographic assay for Trypanosoma cruzi infection using whole blood in Sucre, Bolivia

Paul Roddy^*, Javier Goiri, Laurence Flevaud, Pedro Pablo Palma, Silvia Morote, Nines Lima, Luis Villa, Faustino Torrico, and Pedro Albajar-Viñas

Médecins Sans Frontières – Spain, Barcelona, Spain; Centro Universitario de Medicina Tropical - Facultad de Medicina, Universidad Mayor de San Simon, Cochabamba, Bolivia; Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz - Fiocruz, Rio de Janeiro, Brazil

^* To whom correspondence should be addressed. Email: paul.roddy{at}barcelona.msf.org.

Laboratory and clinical diagnostic classification of seropositive individuals, followed by treatment and supportive therapy, is an established component of Chagas disease control in endemic areas. However, most Chagas-infected patients live in remote areas where neither equipped laboratories nor skilled human resources are widely available. Employing a rapid diagnostic test (RDT), when using whole blood samples, is the best-option for Chagas disease control. A high sensitivity and specificity for the Chagas Stat-Pak^TM RDT (Chembio Diagnostic Systems, Inc., Medford, NY) has been reported when assayed with serum and plasma but its validity for the detection of antibodies to Trypanosoma cruzi infection in whole blood is unknown.

This cross-sectional study measured the sensitivity and specificity of the Chagas Stat-Pak^TM when using whole blood and conventional serological assays as a comparison. The inter-observer reliability in the interpretation of the Chagas Stat-Pak^TM results and ‘ease of use’ criterion needed to perform the Chagas Stat-Pak^TM and conventional assays were also measured.

The Chagas Stat-Pak^TM yielded a high specificity [99.0%, (95%CI: 98.4%-99.4%)] but a relatively low sensitivity [93.4%, (95%CI: 87.4%-97.1%)]. The inter-observer reliability was excellent [kappa(n=1,913)= .999,(p<.0001)] and quantified ‘ease of use’ criterion suggested that the RDT is simple to perform.

Despite the distinguished attributes of the Chagas Stat-Pak^TM, it is not an ideal diagnostic test for the population investigated in this study due to its relatively low sensitivity and high cost. The RDT manufacturer is called upon to improve the test if the international community hopes to make progress in controlling Chagasic infections in endemic areas.

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