From the Guidelines
No, QuantiFERON-TB Gold is not a nucleic acid amplification test (NAAT) for tuberculosis. It is an interferon-gamma release assay (IGRA) that detects cell-mediated immune responses to TB antigens in blood samples. Unlike NAATs which directly detect TB bacterial DNA or RNA, QuantiFERON-TB Gold works by measuring the amount of interferon-gamma released by T-cells when exposed to specific TB antigens (ESAT-6, CFP-10, and TB7.7) 1. This test is primarily used to diagnose latent TB infection rather than active disease. The procedure involves collecting blood samples in specialized tubes containing TB antigens, incubating them for 16-24 hours, and then measuring interferon-gamma production using an enzyme-linked immunosorbent assay (ELISA).
Key Points
- QuantiFERON-TB Gold is an IGRA, not a NAAT 1
- It detects cell-mediated immune responses to TB antigens in blood samples
- The test is used to diagnose latent TB infection, not active disease
- It offers advantages over the traditional tuberculin skin test, including requiring only one patient visit and being unaffected by BCG vaccination 1
Clinical Use
QuantiFERON-TB Gold can be used in all circumstances where the tuberculin skin test (TST) is currently used, including contact investigations, evaluation of recent immigrants, and sequential-testing surveillance programs for infection control 1. However, it is essential to follow the guidelines and recommendations for using IGRAs, as outlined in the updated guidelines for using interferon gamma release assays to detect Mycobacterium tuberculosis infection - United States, 2010 1.
Important Considerations
- The test's ability to predict who will eventually develop TB disease has not been determined 1
- Additional research is needed to focus on the value and limitations of IGRAs in situations of importance to medical care or tuberculosis control 1
From the Research
Quantiferon TB Gold as a TB NAAT Test
- Quantiferon TB Gold is not a nucleic acid amplification test (NAAT) for tuberculosis (TB) 2, 3, 4.
- It is an interferon-gamma release assay (IGRA) that measures the immune response to TB infection 2, 4.
- NAAT tests, such as Xpert MTB/RIF, detect the genetic material of Mycobacterium tuberculosis directly from clinical specimens 5.
- Quantiferon TB Gold has its own strengths and limitations, and its use is recommended for detecting latent TB infection (LTBI) in certain populations 3, 4, 6.
Comparison with NAAT Tests
- Xpert MTB/RIF is a WHO-recommended NAAT test for detecting TB and rifampicin resistance in sputum specimens 5.
- The sensitivity and specificity of Xpert MTB/RIF vary across different types of extrapulmonary specimens, but it is generally accurate for detecting rifampicin resistance 5.
- Quantiferon TB Gold Plus, a newer version of the test, has been shown to be more sensitive than the original Quantiferon TB Gold for detecting M. tuberculosis infection 6.
Clinical Use
- The choice of test for TB diagnosis depends on various factors, including the clinical presentation, risk factors, and availability of resources 3, 4, 5.
- Quantiferon TB Gold and NAAT tests like Xpert MTB/RIF can be used in combination with other diagnostic tools to improve the accuracy of TB diagnosis 3, 5.
- Healthcare providers should consider the strengths and limitations of each test when selecting a diagnostic approach for TB 2, 3, 4, 6, 5.