Loop-mediated isothermal amplification assay for rapid and sensitive diagnosis of tuberculosis

Objectives: Loop-mediated isothermal amplification (LAMP) is a newly developed molecular method that can be performed isothermally. We developed and evaluated a LAMP assay using novel primers to diagnose tuberculosis directly from clinical samples. Materials: Primers were designed to amplify the specific novel esat-6 gene target of Mycobacterium tuberculosis (MTB). Quantitated DNA was used to determine analytical sensitivity and specificity was evaluated by testing 29 NTM and 37 other bacterial species. After standardization, its sensitivity and specificity were evaluated on samples from 118 TB suspected and 31 non-TB patients and compared it with smear, culture and mPCR methods. Results: LAMP was able to detect 5 fg DNA (one MTB) within 21 min and found to be 10 times more sensitive than mPCR and showed 100% specificity against NTM and other bacterial species. In clinical samples, LAMP showed highest MTB detection rate (52.5%) as compared to mPCR (44%) and culture (30.5%). On culture positive and mPCR positive samples, the sensitivity of LAMP was found to be 100% (95% CI 90.2-100) and 96.1% (95% CI 86.7-99.5) respectively with 93.5% (95% CI 78.5-99.2) of overall specificity. Conclusion: LAMP was found to be more sensitive than culture and mPCR for the detection of MTB. It showed specificity comparable to mPCR but was rapid and cost effective. (C) 2014 The British Infection Association. Published by Elsevier Ltd. All rights reserved.