Polymerase Chain Reaction: An Important Tool for Early Diagnosis of Leptospirosis Cases

Various diagnostic methods like Microscopic Agglutination Test (MAT), IgM ELISA, Isolation of Leptospira from the clinical specimen, Rapid leptocheck tests etc., are available for diagnosis of leptospirosis. Polymerase Chain Reaction (PCR) is used for diagnosis of various diseases of infectious origin including leptospirosis but there is paucity of data about comparison of PCR with other available method of diagnosis of leptospirosis.

The aim of the study was to detect the leptospiral DNA by PCR method and to compare the results of PCR with other available diagnostic methods used for diagnosis of suspected leptospirosis cases in acute phase of illness.

A total of 207 blood samples were obtained from suspected patients of leptospirosis admitted in New Civil Hospital, a tertiary care hospital in South Gujarat, during the period of July 2008 to November 2008. These blood samples were subjected to Rapid leptocheck, IgM ELISA, MAT test to detect (IgG or IgM) antibody level, Leptospira culture and PCR.

In early phase of the disease, Rapid leptocheck test gave 44% detection, but along with PCR seropositivity reached upto 71%. Detection rate by IgM ELISA was 59% which increased to 80% with PCR. By MAT seropositivity was 57% but combined seropositivity of MAT with PCR was 78%. Sensitivity and specificity of PCR as compared to MAT (Gold standard) was 52% and 79% respectively. Leptospira was not growing in culture.

In present study, PCR picked up to 50% of cases which were negative by other serological tests so these finding suggest that PCR should be used routinely in acute phase of disease.