Molecular detection of rifampicin resistance in Mycobacterium tuberculosis: An urban study

Objective: The detection of multi-drug resistant tuberculosis (MDR-TB) by broth method requires eight weeks. Molecular technique shortens the duration and it is able to detect the resistant gene. The objective of this study was to determine the feasibility of using molecular technique to detect MDR-TB compared to broth method. Materials and methods: Samples were collected from 726 patients suspected to have tuberculosis throughout the year 2008 in Universiti Kebangsaan Malaysia Medical Centre (UKMMC). Growth on Lowenstein-Jensen media were confirmed as Mycobacterium tuberculosis using BDProbeTec^™ ET Mycobacterium and susceptibility testing was performed using BACTEC ^™ MGIT^™ 960. The 411bp fragment of rpo gene was amplified and sequenced. Results: Fifty of the 726 samples (6.89%) grew Mycobacterium tuberculosis. MDR was detected in four of the 50 (8%) isolates of Mycobacterium tuberculosis. The sensitivity of molecular technique in detecting MDR-TB was 25% with a specificity of 100%. The positive predictive value was 100% whereas negative predictive value was 89.66%. Conclusion: Molecular technique was not an effective screening test for MDR-TB due to the low sensitivity.