Rapid Molecular Detection Test for Mycobacterium Tuberculosis Infection with Rifampin Resistance

Available diagnostic methods (e.g., cell culture, microscopy) for TB are lengthy and can take days to weeks to confirm or rule out the presence of TB and antibiotic resistance. Consequently, infected patients could remain untreated and continue to spread disease. Rapid detection of TB, including drug-resistant TB, is a global priority.1

Sputum-smear microscopy, the most commonly used diagnostic test for TB, is inexpensive but relatively insensitive and cannot test for drug resistance.1 Diagnosis using culture for Mycobacterium tuberculosis is the current gold standard and can differentiate between drug-sensitive and drug-resistant strains.2 The culture method is highly sensitive, but results take a few weeks to process, with further culture testing for multidrug-resistant TB requiring an additional several weeks for results.1

Xpert® MTB/RIF (Mycobacterium tuberculosis/rifampicin Cepheid, Inc., Sunnyvale, CA, USA) is a novel molecular test that purportedly diagnoses rifampicin-resistant TB (i.e., standard first-line antibacterial treatment) within a few hours.1 The Xpert MTB/RIF test runs on Cepheid's GeneXpert® system and is a fully automated real-time polymerase chain reaction that simultaneously detects both TB and resistance to rifampicin by analyzing a particular TB gene (rpoB) known to be targeted by the drug.3 To process a patient's sputum sample, a technician treats the sample and transfers it into a single-use cartridge preloaded with the appropriate reagents. The technician then inserts the cartridge into...