LEPTO Dipstick: a rapid and simple method for serodiagnosis of acute leptospirosis

Abstract

The LEPTO Dipstick assay is a newly developed test for the diagnosis of leptospirosis and uses a broadly reactive antigen for detecting IgM antibodies. The test was evaluated in the Andaman and Nicobar Islands, using 867 serum samples from known cases of leptospirosis and controls. The efficacy of IgM ELISA was also tested for comparison. The LEPTO Dipstick had a sensitivity of 78.7%, a specificity of 88.3% and a positive predictive value of 91.0%. The test had a good level of agreement with the standard criteria for diagnosis using paired microscopic agglutination tests (kappa = 0.64). These indices were similar to those of IgM ELISA (sensitivity 78.5%, specificity 87.6%, positive predictive value 90.5%, kappa 0.63). Both the LEPTO Dipstick and IgM ELISA had the highest sensitivity during the second, third and fourth weeks of illness (87.6% and 88.2%, respectively). Sensitivities during the first week and after 4 weeks were relatively low but acceptable. The test is very easy to perform and does not require any special skills for its performance. The reagents and dipsticks have a long shelf-life even at room temperature. As the test can be performed without the aid of sophisticated equipment, it is suitable for use at the peripheral level as a rapid screening test for the diagnosis of leptospirosis.