TB and Rifampicin Resistance Diagnosed in Remote Regions

A molecular test has succeeded in diagnosing tuberculosis (TB) and rifampicin resistance in remote and resource-poor regions of the world.

The automated molecular test for Mycobacterium tuberculosis (MTB) and resistance to rifampicin (RIF) is called the Xpert MTB/RIF. It uses heminested real-time polymerase chain reaction (PCR) assay to amplify an MTB-specific sequence of the rpoB gene. This is probed with molecular beacons for mutations within the rifampicin-resistance determining region.

The test could dramatically improve outcomes for world's high-risk TB patients. A study compared the sensitivity and specificity of Xpert MTB/RIF to the best available reference standards in the diagnosis of 1,730 patients with suspected drug-sensitive or multi drug-resistant pulmonary tuberculosis (TB) at five centers in Peru, Azerbaijan, South Africa, and India.

Testing was carried out on the GeneXpert MTB/RIF test platform, which integrates sample processing and PCR in a disposable plastic cartridge containing all reagents required for bacterial lysis, nucleic acid extraction, amplification, and amplicon detection.

The study concluded that Xpert MTB/RIF provided sensitive and specific detection of tuberculosis and rifampicin resistance (a critical marker of multidrug resistance) directly from untreated sputum specimens in less than two hours.

An article in the September 1, 2010, New England Journal of Medicine (NEJM) described the test, which was developed by Cepheid (Sunnyvale, CA, USA), and funded and led by the Foundation for Innovative New Diagnostics (FIND; Switzerland).

Rapid diagnosis of Mycobacterium tuberculosis is vital in areas such as sub-Saharan Africa and Southeast Asia due to the close connection between human immunodeficiency virus (HIV) and TB. The most commonly used diagnostic tool is sputum microscopy, which often delivers poor sensitivity in patients suffering from TB.

Related Links:
Cepheid
Foundation for Innovative New Diagnostics