Loop-mediated isothermal amplification assay as a sensitive diagnostic tool for Leishmania donovani infections in Sri Lanka

Abstract

Introduction: Cutaneous leishmaniasis (CL) in Sri Lanka is caused by Leishmania donovani MON 37. Confirmation of diagnosis is done through microscopy, either directly or after in vitro culture. Molecular diagnostic methods are sensitive, but require well established laboratories. Loop mediated isothermal amplification assay (LAMP) is rapid, specific for parasite speciesspecific DNA amplification, and requires only basic laboratory equipment. The aim of the study was to determine the potential utility of LAMP to diagnose leishmaniasis.

Methods: Thirty one patients clinically diagnosed as CL were enrolled in the study. Light microscopy, a widely used and universally accepted method was used as the reference standard for confirmation of diagnosis.

Results: LAMP was positive for 19/23 microscopically positive patients, yielding a sensitivity of 82.6%. Specificity of the LAMP assay was 100% and the positive and negative predictive values were 100% and 66% respectively. The average time taken for the LAMP assay was 1 hour and 40 minutes and the cost per sample was about SLR 2 000, which was approximately half the time and cost of a nested PCR (polymerase chain reaction).

Conclusions: LAMP could be considered a potentially useful diagnostic tool for leishmaniasis.