TB GeneXpert (RT-PCR)

Function

The TB GeneXpert is a molecular test that uses Real-Time Polymerase Chain Reaction (RT-PCR) to detect the DNA of Mycobacterium tuberculosis (MTB). Simultaneously, it identifies mutations in the rpoB gene, which are associated with resistance to Rifampicin, the most important first-line TB drug.

Why it is Ordered

It is used for the rapid diagnosis of pulmonary tuberculosis, especially in patients suspected of having drug-resistant TB or those co-infected with HIV. Unlike traditional cultures which take weeks, GeneXpert provides results in under two hours.

Associated Conditions

• Pulmonary Tuberculosis: Active infection in the lungs.
• Multidrug-Resistant TB (MDR-TB): TB that does not respond to standard treatments.
• Extrapulmonary TB: Use of the test on lymph node tissue or CSF for non-pulmonary infections.

Clinical Importance

GeneXpert has revolutionized TB control by allowing for immediate initiation of appropriate therapy. Early detection of Rifampicin resistance ensures that patients are not started on ineffective treatments, thereby reducing the spread of resistant strains in the community.