MTB Direct PCR

• Volume of at least 5 ml. (5-10 ml preferred). 
• First choice specimen:A specimen from a positive AFB Smear
• Second choice:A first morning specimen for PCR

1. Sputum sediment: Store resuspended sediments at 2–8 °C for up to seven days.
2. Raw sputum:
   • Transport and store specimens at 2–8 °C before processing.
   • sputum specimens can be stored at a maximum of 35 °C for up to three days and then at 2–8 °C for an additional seven days.

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 sputum sediment 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 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 is appropriate 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.