The GeneXpert MTB/RIF system is a fully automated nested real-time PCR system, which detects MTBC DNA in smear positive and negative sputum samples. It simultaneously identifies mutations in the rpoB gene, which is associated with rifampicin resistance.
The GeneXpert MTB/RIF system consists of the instrument, a computer, a barcode scanner and requires single-use disposable Xpert MTB/RIF cartridges that contain assay reagents. Following a 3-step sample preparation in the laboratory, the specimen is transferred into the MTB/RIF cartridge and entered into the GeneXpert instrument. By starting the test on the system software, the GeneXpert automates all following steps, including sample work-up, nucleic acid amplification, detection of the target sequence and result interpretation. The primers in the Xpert MTB/RIF assay amplify a portion of the rpoB gene containing the 81-base pair “core” region. The probes are able to differentiate between the conserved wild-type sequence and mutations in the core region that are associated with resistance to RIF.