" Rapid Detection of Mycobacterium in sputum samples in Nepal by Loop-Mediated Isothermal Amplification (LAMP)

Abstract

Mycobacterium tuberculosis still remains a substantial global threat. The conventional biochemical tests for identification of mycobacterial species are time-consuming. Loop-Mediated Isothermal Amplification (LAMP) provides new possibilities of other tests requirements for direct detection of M. tuberculosis, M. avium complex and M. kansasii in sputum samples. This study was carried out from February 2009 to March 2010 based at German Nepal Tuberculosis Project, Everest International Clinic and Research Center in collaboration with Central Department of Microbiology and Osaka Perfectural Institute of Public Health Japan. A total of 135 (100%) sputum specimens (103 from new suspected pulmonary tuberculosis patients and 32 follow up MDR patients) were included in this study for comparative study of Microscopy, culture and LAMP. Among them, 60 (44.4%) were microscopy positive. Similarly 68 (50.3%) sputum specimens were positive by culture and 71 (52.5%) sputum specimens were positive by LAMP. Out of 71 (100%) total LAMP positive cases, 70 (98.5%) were positive with M. tuberculosis primer and remaining 1(1.4%) was positive with M. intracellular primer. None of the M. avium and M. kansasii cases were found from the samples that were included in this study. With reference to microscopy result, the sensitivity and specificity of LAMP were 96.6%and 82.6% respectively. Predictive value of positive test was 81.7%, predictive value of negative test was 96.8%, percentage of false negative was 3.3% and percentage of false positive was 17.3%.Similarly, while comparing the LAMP result with culture as gold standard, the sensitivity of LAMP was 97.5%, specificity was 92.5%, predictive value of positive test was 92.9%, predictive value of negative test was 96.8%, percentage of false positive was 7.4% and percentage of false negative was 2.9%. This study showed that LAMP is sensitive and specific molecular technique, which can be used effectively for the diagnosis thus facilitating the effective treatment and case management of tuberculosis and other atypical mycobacterial infection.