Diagnostic Evaluation of GeneXpert MTB/RIF Assay for the Detection of Rifampicin Resistant Mycobacterium tuberculosis among Pulmonary Tuberculosis Patients in Bangladesh

Background: The emergence of multidrug resistant tuberculosis (MDR-TB) and extensively drug- resistant tuberculosis (XDR-TB) has highlighted the need for early accurate detection and drug susceptibility. Objective: The purpose of the present study was to evaluate the accuracy of GeneX-pert MTB/RIF assay for the detection of Mycobacterium tuberculosis and rifampicin resistance. Methodology: This cross sectional study was done in the Department of Microbiology at Sir Salimullah Medical College, Dhaka and National Institute of Chest Disease & Hospital (NIDCH), Dhaka during the period of January 2014 to December 2014 for a period of 1 (one) year. Sputum samples from suspected MDR-TB patients were collected by purposive sampling technique from OPD of Sir Salimullah Medical College (SSMC) and NIDCH. Microscopy, liquid culture in liquid MGIT 960 media and GeneXpert MTB/RIF were done for MTB diagnosis and detection of rifampicin resistance. MGIT 960 media were also used for determination of drug resistance. Result: Liquid culture yielded higher growth (68%) from 100 samples while GeneXpert MTB assay showed similar result (67% positive and 33% negative). Drug susceptibility test in MGIT 960 media showed that out of 68 positive cases Rifampicin resistant cases were 15 (22.05%) whereas GeneXpert MTB assay detected 14 (20.89%) were Rifampicin resistant out of 67 MTB positive samples. When compared to liquid culture the calculated sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and accuracy of GeneXpert MTB were 98.52%, 100%, 96.96%, 100% and 99%. Conclusion: GeneXpert MTB/RIF assay is high detection rate of pulmonary tuberculosis and multidrug resistant tuberculosis.