Utility of GenoType MTBDRPlus Assay for Direct Detection and Drug Susceptibility Testing of Mycobacterium tuberculosis from Probable Tuberculous Meningitis Patients

Aims: To evaluate GenoType® MTBDRplus line probe assay as a diagnostic tool for detection of Mycobacterium tuberculosis and drug susceptibility testing from cerebrospinal fluid of probable tuberculous meningitis patients.
Study Design: A prospective, double blind study.
Place and Duration of study: Dept. of Microbiology and Neurology, Institute of Human Behavior and Allied sciences, Delhi, India between February 2014 to October 2014.
Methodology: Cerebrospinal fluid collected from 107 probable meningitis patients with diagnostic score >10 were subjected to smear microscopy, automated liquid culture (BACTEC MGIT 960) and Polymerase chain reaction (IS6110). All the samples were also subjected to GenoType® MTBDRplus line probe assay for detecting M. tuberculosis and drug susceptibility. Drug susceptibility testing of all the M. tuberculosis isolates was done by BACTEC MGIT 960 and GenoType® MTBDRplus line probe assay.
Results: The sensitivity, specificity of the assay for M. tuberculosis detection was 49.5%, 100% against clinical diagnosis as reference standard and 68.9%, 100% against definitive diagnosis as reference standard. A diagnostic accuracy of 56.8% (kappa 0.22), 75% (kappa 0.46), were seen in patients with probable and confirmed diagnosis respectively. The drug susceptibility results for Isoniazid and Rifampicin could be delineated in only 39.2% of patients.
Conclusion: This assay proved to have better sensitivity, diagnostic accuracy than smear microscopy and automated liquid culture for early detection of M. tuberculosis from probable tuberculous meningitis patients and has comparable sensitivity to culture (39.2%) for detection of drug susceptibility (though on different isolates). Rapid turnaround time and user friendliness makes it an acceptable assay for simultaneous early detection of M. tuberculosis and its drug susceptibility for better patient management.