Sensitivity and specificity of an operon immunochromatographic test in serum and whole-blood samples for the diagnosis of Trypanosoma cruzi infection in Spain, an area of nonendemicity

Abstract

Trypanosoma cruzi infection is an imported parasitic disease in Spain, and the majority of infected individuals are in the chronic phase of the disease. This study evaluated the sensitivity and specificity of the Operon immunochromatographic test (ICT-Operon; Simple Stick Chagas and Simple ChagasWB[whole blood]; Operon S.A., Spain) for different biological samples. Well-characterized serum samples were obtained from chagasic patients (n=63), nonchagasic individuals (n=95), visceral leishmaniasis patients (n=38), and malaria patients (n=55). Noncharacterized specimens were obtained from Latin American immigrants and individuals at risk with a clinical and/or epidemiological background: these specimens were recovered serum or plasma samples (n=450), whole peripheral blood (n=94), and capillary blood (n=282). The concordance of the results by enzyme-linked immunosorbent assay and indirect immunofluorescence test was considered to be the "gold standard" for diagnosis. Serum and plasma samples were analyzed by Stick Chagas, and whole blood was analyzed by Simple Chagas WB. The sensitivity and specificity of the ICT-Operon in well-characterized samples were 100% and 97.9%, respectively. No cross-reactivity was found with samples obtained from visceral leishmaniasis patients. In contrast, a false-positive result was obtained in 27.3% of samples from malaria patients. The sensitivities of the rapid test in non-characterized serum or plasma, peripheral blood, and capillary blood samples were 100%, 92.1%, and 86.4%, respectively, while the specificities were 91.6%, 93.6%, and 95% in each case. ICT-Operon showed variable sensitivity, depending on the kind of sample, performing better when serum or plasma samples were used. It could therefore be used for serological screening combined with any other conventional test. Copyright © 2012, American Society for Microbiology. All Rights Reserved.