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The Xpert® MTB/RIF Assay, performed on the GeneXpert® Instrument Systems, is a qualitative, nested realtime polymerase chain reaction (PCR) in vitro diagnostic test for the detection of Mycobacterium tuberculosis complex DNA in raw sputum or concentrated sputum sediment prepared from induced or expectorated sputum. In specimens where Mycobacterium tuberculosis complex) is detected, the Xpert MTB/RIF Assay also detects the rifampin-resistance associated mutations of the rpoB gene. The Xpert MTB/RIF Assay is intended for use with specimens for whom there is clinical suspicion of tuberculosis (TB) and who have received no antituberculosis therapy, or less than three days of therapy. This test is intended as an aid in the diagnosis of pulmonary tuberculosis when used in conjunction with clinical and other laboratory findings. An Xpert MTB/RIF Assay result of "MTB NOT DETECTED" from either one or two sputum specimens is highly predictive of the absence of M. tuberculosis complex bacilli on serial fluorescent acid-fast sputum smears from patients with suspected active pulmonary tuberculosis and can be used as an aid in the decision of whether continued airborne infection isolation (AII) is warranted in patients with suspected pulmonary tuberculosis. The determination of whether testing of either one or two sputum specimens for decisions regarding removal from AII should be based on specific clinical circumstances and institutional guidelines. Clinical decisions regarding the need for continued AII should always occur in conjunction with other clinical and laboratory evaluations and Xpert MTB/RIF Assay results should not be the sole basis for infection control practices. The Xpert MTB/RIF Assay must always be used in conjunction with mycobacterial culture to address the risk of false negative results and to recover organisms when MTB-complex is present for further characterization and drug susceptibility testing. However, decisions regarding the removal of patients from AII need not wait for culture results. Sputum specimens for TB culture, AFB smear microscopy, and Xpert MTB/RIF Assay testing should follow CDC recommendations with regard to collection methods and time frame between specimen collection. The Xpert MTB/RIF Assay does not provide confirmation of rifampin susceptibility since mechanisms of rifampin resistance other than those detected by this device may exist that may be associated with a lack of clinical response to treatment. Specimens that have both MTB-complex DNA and rifampin-resistance associated mutations of the rpoB gene detected by the Xpert MTB/RIF Assay must have results confirmed by a reference laboratory. If the presence of rifampin-resistance associated mutations of the rpoB gene is confirmed, specimens should also be tested for the presence of genetic mutations associated with resistance to other drugs. The Xpert MTB/RIF Assay should only be performed in laboratories that follow safety practices in accordance with the CDC/NIH Biosafety in Microbiological and Biomedical Laboratories publication and applicable state or local regulations.

The Xpert MTB/RIF Assay is a qualitative, automated, in vitro diagnostic test for qualitative detection of Mycobacterium tuberculosis (MTB) complex DNA in raw sputum samples or in concentrated sputum sediments prepared from induced or expectorated sputa that are either acid-fast bacilli (AFB) smear positive or negative. The assay is performed on the Cepheid GeneXpert Instrument Systems. The Xpert MTB/RIF Assay on the GeneXpert Instrument System automates and integrates sample preparation, nucleic acid amplification, and detection of the target sequences in simple or complex samples using real-time PCR. The system consists of an instrument, personal computer, and preloaded software for running the tests and viewing the results. The system requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, cross-contamination between samples is minimized. The Xpert MTB/RIF Assay includes reagents for the detection of MTB and Rifampin (RIF) resistance from raw sputum samples and in prepared sputum sediments. A Sample Processing Control (SPC) and a Probe Check Control (PCC) are also included in the cartridge. The SPC is present to control for adequate processing of the target bacteria and to monitor for the presence of inhibitors in the PCR reaction. The Probe Check Control (PCC) verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity, and dve stability. The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems, the GeneXpert Infinity-48 System, the GeneXpert Infinity-48s, and the GeneXpert Infinity-80 System, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR tests. Each module contains a syringe drive for dispensing fluids (i.e., the syringe drive activates the plunger that works in concert with the rotary valve in the cartridge to move fluids between chambers), an ultrasonic horn for lysing cells or spores, and a proprietary I-CORE® thermocycler for performing real-time PCR and detection.

The Xpert® MTB/RIF Assay, performed on the GeneXpert® Instrument Systems, is a qualitative, nested real-time polymerase chain reaction (PCR) in vitro diagnostic test for the detection of Mycobacterium tuberculosis complex DNA in raw sputum or concentrated sediments prepared from induced or expectorated sputum. In specimens where Mycobacterium tuberculosis complex (MTB-complex) is detected, the Xpert MTB/RIF Assay also detects the rifampin-resistance associated mutations of the rpoB gene. The Xpert MTB/RIF Assay is intended for use with specimens from patients for whom there is clinical suspicion of tuberculosis (TB) and who have received no antituberculosis therapy, or less than 3 days of therapy. This test is intended as an aid in the diagnosis of pulmonary tuberculosis when used in conjunction with clinical and other laboratory findings. The Xpert MTB/RIF Assay does not provide confirmation of rifampin susceptibility since mechanisms of rifampin resistance other than those detected by this device may exist that may be associated with a lack of clinical response to treatment. Specimens that have both MTB-complex DNA and rifampin-resistance associated mutations of the rpoB gene detected by the Xpert MTB/RIF Assay must have results confirmed by a reference laboratory. If the presence of rifampin-resistance associated mutations of the rpoB gene is confirmed, specimens should also be tested for the presence of genetic mutations associated with resistance to other drugs. The Xpert MTB/RIF Assay must be used in conjunction with mycobacterial culture to address the risk of false negative results and to recover the organisms for further characterization and drug susceptibility testing. The Xpert MTB/RIF Assay should only be performed in laboratories that follow safety practices in accordance with the CDC/NIH Biosafety in Microbiological and Biomedical Laboratories publication and applicable state or local regulations.

The Xpert® MTB/RIF Assay is an automated in vitro diagnostic test for the qualitative detection of MTB-complex DNA and the genetic mutations associated with rifampin (Rif) resistance in raw sputum samples or concentrated sputum sediments from patients for whom there is clinical suspicion of TB and who have received no antituberculosis therapy, or less than 3 days of therapy. The primers in this test amplify a portion of the rpoB gene containing the 81 base pair core region. The probes are designed to differentiate between the conserved wild-type sequence and mutations in the core region that are associated with Rif resistance. The assay is performed on Cepheid GeneXpert® Instrument Systems. The Xpert® MTB/RIF Assay includes single-use disposable cartridges and sample reagent for sample preparation. The Xpert® MTB/RIF Assay cartridges contain reagents for the detection of MTB-complex DNA and Rif resistance associated mutations. A Sample Processing Control (SPC) and a Probe Check Control (PCC) are also included in the cartridge. The SPC is present to control for adequate processing of the target microorganism and to monitor the presence of inhibitors in the PCR reaction. The Probe Check Control (PCC) verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity and dye stability. Sputum specimens are collected according to the institution's standard procedures and transported to the GeneXpert® Instrument System area. For raw sputum, Sample Reagent is added to the sample (2:1, v:v). Sample Reagent is added to the resuspended sputum sediment (1.5 mL Sample Reagent to 0.5 mL suspension or 3:1, v:v, for larger volumes of sediment suspension). For both specimen types, the solution is shaken vigorously to mix, and then incubated at 20-30℃ for 15 minutes. Using the transfer pipette provided, the specimen is transferred to the open port of the Xpert® MTB/RIF Assay cartridge. The user initiates a test from the system user interface, the Xpert® MTB/RIF Assay cartridge is loaded onto the GeneXpert® Instrument System platform, which performs hands-off, automated sample processing, and real-time PCR for detection of DNA, Summary and detailed test results are obtained in approximately 2 hours and are displayed in tabular and graphic formats. The Xpert® MTB/RIF Assay simultaneously detects MTB-complex and the genetic mutations associated with rifampin resistance by amplifying a MTB-complex specific sequence of the rpoB gene, which is probed with five molecular beacons (Probes A - E) for mutations within the rifampin-resistance determining region (RRDR). Each molecular beacon is labeled with a different fluorophore. The valid maximum cycle threshold (Ct) of 39.0 for Probes A, B and C and 36.0 for Probes D and E are set for data analysis. - "MTB DETECTED", is reported when at least two probes result in Ct values within the valid range and a delta Ct min (the smallest Ct difference between any pair of probes) of less than 2.0. - "Rif Resistance NOT DETECTED" is reported if the delta Ct max (the Ct difference between the earliest and latest probe) is ≤4.0. - "Rif Resistance DETECTED" is reported if the delta Ct max is >4.0. - "Rif Resistance INDETERMINATE" is reported when the following two conditions are met: - 1. the Ct value of any probe exceeds the valid maximum Ct (or is zero, i.e. no threshold crossing); and - 2. the earliest rpoB Ct value is greater than [(Valid maximum Ct of probe in condition1) - (delta Ct max cut-off of 4.0)] - "MTB NOT DETECTED" is reported when there is only one or no positive probe. All assay settings are included as automatic calculations in the Xpert® MTB/RIF Assay protocol and cannot be modified by the user.