Are WHO approved nucleic acid amplification tests causing large-scale "false identification" of rifampicin-resistant tuberculosis?: Programmatic experience from south india.

Introduction: The nucleic acid amplification tests (NAATs): Line probe assay and GeneXpert (Xpert) have evolved as the primary tool for identification of rifampicin (RIF)-resistant (RR) tuberculosis (TB) worldwide, primarily because of the ease and speed. We rechecked RR isolates identified by NAATs from presumptive RR TB cases belonging to South India by the Revised National TB Control Program, India using multiple RIF concentrations on Bactec MGIT system and compared the mutation patterns with the resistance levels.

Methodology: Standard protocol for Bactec MGIT system as given by the manufacturer modified for the multiple RIF concentrations was used.