Evaluation of Geno Type MTBDRplus Line Probe Assay for Early Detection of Drug Resistance in Tuberculous Meningitis Patients in India

Background: Molecular methods which allow for rapid and reliable detection of drug resistance have yet not been sufficiently evaluated for timely management of patients with tuberculous meningitis. Aims: We aimed to evaluate Geno Type MTBDRplus line probe assay for early detection of drug resistance in Mycobacterium tuberculosis isolates and CSF samples of confirmed tuberculous meningitis patients. Settings and Design: This was a multicentric prospective study carried out from July 2011 to December 2013 in tertiary care hospitals of Delhi. Materials and Methods: The assay was performed on 89 M. tuberculosis isolates and 31 direct CSF samples from microbiologically confirmed tuberculous meningitis patients. The sensitivity and specificity of this assay was calculated in comparison to drug susceptibility testing by BACTEC MGIT 960 system. Results: The sensitivity, specificity for detection of resistance to Isoniazid was 93%, 97% and to Rifampicin was 80%, 98.8%, respectively by this assay in comparison with the phenotypic drug susceptibility testing. The line probe assay could detect M. tuberculosis in 55% of CSF samples from patients with microbiologically confirmed tuberculous meningitis. Only 5/89 isolates (5.6%) were resistant to both Isoniazid and Rifampicin while 9/89 (10%) isolates were additionally resistant to Isoniazid. Resistance to any of the drugs, namely Isoniazid, Rifampicin, Streptomycin or Ethambutol, was seen in 24.7% of strains. Conclusion: The line probe assay has a good sensitivity and specificity for detection of drug resistance to Isoniazid and Rifampicin in M. tuberculosis culture isolates. However, this assay has limited role in detection of M. tuberculosis and drug resistance from direct samples with confirmed diagnosis of tuberculous meningitis.