Evaluation of indirect drug susceptibility testing using the MODS assay for the detection of XDR-TB in China.

Methods: The First Affiliated Hospital of Nanchang University and the Chest Hospital of Jiangxi Province, Jiangxi, China.

Objective: To assess the performance and feasibility of the microscopic observation drug susceptibility (MODS) assay for the simultaneous detection of multidrug-resistant (MDR) and extensively drug-resistant tuberculosis (XDR-TB) in a high-burden, resource-limited setting.

Methods: A total of 208 archived clinical isolates of Mycobacterium tuberculosis were used to compare MODS with the conventional proportion method for the rapid detection of resistance to rifampicin (RMP) and isoniazid (INH), as well as to the second-line drugs ofloxacin (OFX) and kanamycin (KM).

Results: Sensitivity was respectively 94.5%, 91%, 96.2% and 91.5% for RMP, INH, OFX and KM, and specificity was respectively 97.5%, 96%, 100% and 98.7%. Results for MODS were obtained in a median time of 7 days (range 5-17).

Conclusions: The MODS assay offers a simple, rapid, economical and feasible method for the detection of M. tuberculosis resistance to first- and second-line drugs in resource-limited settings.