A pilot study on comparison of rapid immunodiagnostics for confirmation of leptospirosis

Abstract

INTRODUCTION: In Sri Lanka, leptospirosis is mostly diagnosed on clinical grounds. Serological confirmation is not obtainable during the acute stage of the illness. There is a need for rapid immunodiagnostics for confirmation of leptospirosis. Two immunodiagnostic assays, ie: enzyme linkedimmnnosorbent assay (ELISA) and immunochromatographic technique Leptocheck-WB test (LCT) areused to detect leptospira specific IgM antibodies which are prevalent in early stages of acute infections. AIMS: To compare the efficacy of these two rapid immunodiagnostic assays with the microscopic agglutination assay (MAT) to determine their applicability. Methods: A set of sera (n=83) collected in 2010 for which MAT titres were available was used to perform IgMELISAandLCT. RESULTS: Positivity for LCT and IgM ELISA were 55.4% and 48.2% respectively, and both assays detected acute infection by day 3 of the illness. MAT> 400 was used as the reference standard. For LCT, the overall sensitivity, specificity, accuracy, PPV and NPV (86.5%, 75.0%, 79.6%, 69.6% and 89.4% respectively) were higher compared to the respective values for IgM ELISA (50.0%, 62.3%, 57.1%, 50.0%, 62.3%). The highest of these values were observed during the first week for LCT and during the second week for IgM ELISA. The highest agreement was observed between LCT and MAT>400 (p=0.568) and there was a good agreement between LCT and IgM ELISA (p=0.520). CONCLUSIONS: The high sensitivity and specificity, ease of use, and non-requirement of specialized skills and equipment makes LCT a good choice for screening, while IgM ELISA is an appropriate test for confirming acute leptopsirosis.