Study of the prevalence of Multidrug-Resistant Pulmonary Tuberculosis (MDR-TB) in Western Rajasthan using line probe assay

OBJECTIVE: To determine the prevalence of MDR-TB and find out the incidence of drug resistance using molecular diagnostic method. Line probe assay (LPA) is based on the principle of multiplex PCR is used to detect MTB (Mycobacterium tuberculosis) complex as well as its sensitivity to rifampicin and isoniazid. METHOD: This is a hospital-based prospective observational study. The sputum of MDR-TB suspected patients was subjected to Ziehl-Neelsen staining and smear positive samples were analyzed by LPA. Decontamination and digestion of the samples was done using the NALC- NaOH method (as defined in RNTCP guidelines). DNA extraction was done from the decontaminated samples using Geno Lyse kit. After DNA extraction, detection of MTB complex and rifampicin and/or INH resistance was done with the help of line probe assay (LPA) using GenoType ® MTBDRplus version 2.0. RESULTS: Out of the 156 smear-positive sputum samples, 140 samples had LPA valid results. The most common age group of positive TB samples in this study was 30-40 years (26.42%). Twenty-five samples (17.85%) were found to be rifampicin resistant and 22 (15.71%) samples were found resistant to isoniazid. Sixteen patients (11.42%) were detected MDR. Nine patients (6.42%) were monoresistant to rifampicin and six patients (4.28%) were monoresistant to isoniazid. “Sputum positive retreatment cases” had the highest detection rate for MDR TB. CONCLUSION: Line probe assay is an economical and time saving method for the detection of MDR-TB and serves as a lifesaving tool for early diagnosis and treatment. This calls for a widespread national use of this assay. The detection of around 10% ZN-positive patients, who were not showing MTB complex in LPA may be a hidden iceberg for non-tubercular mycobacteria.