Full text loading...
Chapter 7.6 : Nucleic Acid Amplification Procedures for Identification from Specimen
The Xpert MTB/RIF assay, which is performed on the GeneXpert platform, employs an individual plastic cartridge into which a respiratory sample, pretreated with a provided reagent that liquefies the sputum and decreases the viability of mycobacteria (and other bacteria), is added. The cartridge is placed in the GeneXpert instrument, which integrates and automates sputum sample processing, two rounds of nucleic acid amplification, and detection of the target sequences using real-time PCR ( 1 ). The system consists of an instrument, computer, barcode scanner, and preloaded software that controls the process within the cartridge. The system requires single-use disposable GeneXpert cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, cross-contamination between samples is unlikely. The Xpert MTB/RIF Assay includes reagents for the detection of Mycobacterium tuberculosis (MTB) complex and rifampin (RIF) resistance and a sample processing control (SPC) to ensure adequate processing of the target bacteria and to monitor for the presence of inhibitors in the PCR reaction. The Probe Check Control (PCC) verifies that the reagent has dissolved in the diluent, that the PCR tube has filled with the liquid reagent in the cartridge, that the probe is working, and that the dye is stable.