Detection of drug-resistant mycobacterium tuberculosis using Geno Type MTBDRplus assay in smear-positive cases

Background Multidrug-resistance tuberculosis (MDR-TB) has become an annoying health problem with supreme concern in the developing countries. Several methods of detection of MDR-TB have developed over recent years. Objective To investigate the diagnostic accuracy of GenoType MTBDRplus assay in detection of rifampicin (RIF)- and isoniazid (INH)-resistant isolates from sputum specimens of patients with active TB. Patients and methods This is a cross-sectional study. Sputum samples from 50 cases with active TB were collected, and the drug sensitivity test was evaluated by two methods: the standard conventional culture method and the GenoType MTBDRplus assay as a newly developed genotypic (molecular) method. Results The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of GenoType MTBDRplus assay in detection of RIF resistance were 100, 97.5, 90, 100, and 98%, respectively versus 100, 94.4, 87.5, 100, and 96%, respectively, for detection of INH resistance. The prevalence of MDR-TB by genotypic method was 12 versus 8% by conventional culture. On the contrary, drug resistance to either RIF or INH was detected in 28% of cases by the molecular method versus 30% of cases by using conventional culture. Conclusion The diagnostic yield of GenoType MTBDRplus assay for detection of RIF and INH resistance was satisfactory enough to support its alternative use for rapid identification of MDR-TB isolates, facilitating early and proper anti-TB drug regimen.