From the Guidelines
GeneXpert MTB/RIF is a molecular diagnostic test that detects the presence of Mycobacterium tuberculosis (MTB) and tests for resistance to rifampin (RIF) simultaneously. This automated nucleic acid amplification test (NAAT) works by identifying specific DNA sequences of the tuberculosis bacteria through a process called real-time polymerase chain reaction (PCR) 1. The test provides results within approximately 2 hours, making it much faster than traditional TB culture methods which can take weeks. GeneXpert is particularly valuable because it can quickly identify rifampin resistance, which is often a marker for multidrug-resistant tuberculosis (MDR-TB). The test requires minimal technical expertise to perform and has high sensitivity and specificity, especially in patients with positive sputum smears. It can be used with various specimen types including sputum, cerebrospinal fluid, and lymph node samples.
Some of the key features of GeneXpert MTB/RIF include:
- Rapid results: The test provides results within 2 hours, allowing for quick diagnosis and treatment initiation 1.
- High sensitivity and specificity: The test has high sensitivity and specificity, especially in patients with positive sputum smears 1.
- Minimal technical expertise: The test requires minimal technical expertise to perform, making it accessible to a wide range of healthcare settings 1.
- Versatile specimen types: The test can be used with various specimen types, including sputum, cerebrospinal fluid, and lymph node samples 1.
The World Health Organization recommends GeneXpert MTB/RIF as an initial diagnostic test for suspected TB patients, particularly when drug resistance is a concern or in HIV-associated TB cases 1. Overall, GeneXpert MTB/RIF is a valuable tool in the diagnosis and management of tuberculosis, especially in resource-limited settings where traditional culture methods may not be feasible.
From the Research
Overview of GeneXpert MTB/RIF Test
- The GeneXpert MTB/RIF test is a real-time polymerase chain reaction assay used for the simultaneous detection of Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF) 2, 3, 4, 5, 6.
- It is a molecular diagnostic tool that can detect MTB and identify genetic determinants of rifampicin resistance 4.
Diagnostic Accuracy
- The sensitivity and specificity of the GeneXpert MTB/RIF test vary depending on the type of specimen and the presence of MTB 2, 3, 5, 6.
- For respiratory samples, the sensitivity and specificity of the test are high, ranging from 90.2% to 100% and 78.9% to 98.6%, respectively 2, 3, 5, 6.
- For non-respiratory samples, the sensitivity and specificity of the test are lower, ranging from 33.3% to 81.6% and 70.5% to 99.7%, respectively 2, 5, 6.
Detection of Rifampin Resistance
- The GeneXpert MTB/RIF test can detect rifampin resistance in MTB-positive specimens 2, 3, 4, 5, 6.
- The test has been shown to accurately detect rifampin resistance in various studies, with a high degree of accuracy compared to drug susceptibility testing 2, 3, 6.
Clinical Utility
- The GeneXpert MTB/RIF test is a rapid and simple method for diagnosing tuberculosis and detecting rifampin resistance 2, 3, 4, 5, 6.
- It can be used as a "rule-in" test for patients with negative smear results and as a tool for early detection of MTB and rifampin resistance 4.
- The test has been recommended by the World Health Organization (WHO) as a standard molecular biological diagnostic technique for MTB 3.