Abstract

COMPARISON OF THREE RAPID DIAGNOSTIC ASSAYS FOR DIAGNOSIS OF LEPTOSPIROSIS IN A RESOURCE POOR SETTING

Kanchana Kumari Bandara, Chinthika Prabhashinie Gunasekara*, Manjula Manoji
Weerasekera, Nilantha Ranasinghe, Menaka Hapugoda, Chamil Marasinghe and Neluka Fernando

Abstract

Rapid serological diagnostic tests are easy to perform, cost effective and useful as a point-of-care diagnostic in resource-poor areas. This study was conducted to compare the performance of three rapid serodiagnostic tests for detection of leptospirosis in Sri Lanka. Serum of 75 clinically suspected leptospirosis patients between January to December 2013 were tested by three commercial immunochromatographic assays; Leptocheck–WB test, SD Leptospira IgM and SD Leptospira IgG/IgM. Leptospirosis was confirmed by MAT titre ≥400 or by a positive PCR. While 75% patients were clinically suspected of leptospirosis according to the Modified Faine’s Criteria (2012), leptospirosis was confirmed in 65.3% by MAT or PCR. Of the 75 serum specimens tested, IgM was positive by Leptocheck –70.6%, SD IgM – 50.6% and SD IgG/IgM– 53.3%. Leptospirosis was confirmed by MAT in 54.6% and by PCR in 13.3%. The sensitivity, specificity, PPV and NPV based on Bayesian latent class analysis were Leptocheck – 99.1%, 68.1%, 84.1%, 97.9%, SD IgM – 80%, 93.9%, 95.8%, 73.3% and SD IgG/IgM – 98.3%, 88.9%, 89.8%, 98.2%. The kappa values (Leptocheck-0.49, SD IgM–0.46, SD IgG/IgM– 0.45) showed satisfactory agreement with MAT and PCR. False positives and false negatives were seen in all three kits.

Keywords: Leptospirosis, Immunochromatographic assay, MAT, PCR.