Effect of chaotropes in Chagas disease and leishmaniasis cross-reacting serology assays for epidemiological surveys.

INTRODUCTION: Serological cross-reactivity between leishmaniasis and Chagas disease, especially at low titers, leads to difficulties of the seroepidemiological interpretation.

METHODS: We have studied the ability of urea as a chaotrope to select high-avidity antibodies in IgG ELISA, thus reducing low-avidity IgG cross-reactivity in serologically positive samples in both assays.

RESULTS: Using 0.5M urea for diluting the sample efficiently defined leishmaniasis or double infections in high-avidity IgG ELISA and eliminated false-positive results.

CONCLUSIONS: The use of a chaotropic diluting agent is useful for improving the specificity of Chagas disease and leishmaniasis immunoassays.