Using archived samples, we assessed the diagnostic capacity of two commercially available tests (an ELISA IgM
and a rapid immunochromatographic test, ICT) for the detection of Leptospira spp. IgM and IgG antibodies to aid with the
diagnosis of acute leptospirosis in febrile patientsin Thailand. The sensitivities of the ELISA for the detection of IgM and the
rapid immunochromatographic test for the detection of IgG were 60.7% (95% CI, 50.3 to 70.2%), and 83.2% (95% CI 73.9
to 89.6%) respectively. False positive ICT result occurred in one patient with influenza B infection. The positive rates of both
assays were high after the first week of onset of fever up to third weeks of illness.

Keywords: Immunochromatographic assay, ELISA, Leptospirosis