Line Probe Assay as a Rapid Tool for Detection of MDRTB

Aims: To evaluate genotypic Line Probe Assay (LPA) for rapid detection of Multidrug Resistant Tuberculosis (MDRTB) directly from sputum samples in comparison with Drug Susceptibility Testing (DST) on phenotypic MBBacT liquid media.
Study Design: Data analysis from 86 Mycobacterium tuberculosis (MTB) strains was done using SPSS version 17.
Place and Duration of Study: Department of Microbiology, JSS Medical College, Mysore, Karnataka, between January 2011 to January 2012.
Methodology: MDRTB rate detected by LPA assay from 92 samples by noting the mutations in hot spot region of rpoB gene, katG and inhA regulatory region and compared with DST on MBBacT liquid media.
Results: Out of 86 MTB isolates, resistant rates for Rifampicin (RIF) and Isoniazid (INH) were 41.8%, 39.53% by LPA and 45.34%, 55.81% by MBBacT. LPA assay showed sensitivity and specificity as 92.35%, 100% for RIF resistance detection and 70.83%, 100% for INH resistance detection, 94.74%, 100% for MDRTB detection compared to conventional DST results.
Conclusion: This study showed that LPA has high detection rate for RIF resistance. However to improve the detection of INH resistance in MTB strains additional probes are to be included in LPA. LPA has good sensitivity and specificity for MDRTB detection with turnaround time of less than 48 hours.