Abstract

EFFICACY OF DARK FIELD MICROSCOPY AND IGM-ELISA IN THE DETECTION OF LEPTOSPIROSIS

Author(s): Shanmuga Sundaram Rajamani1, Sudha Krishnan2, Shankar Radhakrishnan3

BACKGROUND
Leptospirosis is one of the most serious zoonotic disease. The spectrum of human disease caused by Leptospira is extremely wide, ranging from subclinical infection to a severe syndrome of multi organ infection with high mortality. Dark field microscopy which is considered as a conventional method for detecting Leptospira is still being practiced but MAT was considered to be the gold standard. Alternatives to MAT are the IgM dot-ELISA dipstick test (DST), and the indirect haemagglutination assay (IHA).
AIM
To assess and compare the efficacy levels of dark field microscopy and IgM ELISA in comparison with PCR in diagnosing leptospirosis.
MATERIALS AND METHODS
A cross-sectional study was conducted in our hospital during the period of August 2014 – July 2015. All the patients with more than 12 years of age and symptoms suggestive of Leptospira were included in the study. All patients were subjected to DFM, and ELISA IgM within 48 hours of admission and on 7th day the patients had undergone PCR. The procedure of testing was followed as per the guidelines given in the kit.
RESULTS
The sensitivity for dark field microscopy in detecting Leptospira in comparison with PCR was found to be 92.8% and the specificity was 87%. The positive predictive value was 78.7% and the percentage of false positives was 12.9% whereas for IgM-ELISA the sensitivity, specificity and positive predictive value was 100%, 96.2% and 93.3% and the percentage of false positives is 3.7%. The sensitivity, specificity, PPV and NPV of IgM ELISA was higher when compared to the dark field microscopy and the percentage of false positives was comparatively lesser than the dark field microscopy.
CONCLUSIONS
Leptospirosis being an emerging and usually under diagnosed disease, newer diagnostic tests and rapid case detection particularly during an outbreak becomes the need of the hour and IgM-ELISA would satisfy these things in the detection of Leptospira.