From the Guidelines
If you have a positive QuantiFERON-TB Gold test with a value over 10 IU/mL, you should be considered for treatment of latent tuberculosis infection (LTBI) to prevent progression to active TB disease. According to the CDC recommendations 1, any individual with a positive QFT-G result should be considered for LTBI treatment, taking into account the likelihood of completing treatment under supervision. The standard treatment regimen is typically isoniazid (INH) 300 mg daily for 6-9 months, or a shorter course of isoniazid plus rifapentine once weekly for 12 weeks. Alternative regimens include rifampin 600 mg daily for 4 months.
- Before starting treatment, a chest X-ray is necessary to rule out active TB disease, as treatment differs for active infection.
- During treatment, regular liver function tests are necessary to monitor for medication side effects.
- A high QuantiFERON value (over 10 IU/mL) indicates significant immune response to TB bacteria but doesn't necessarily mean you have active disease or are more contagious.
- However, it does confirm you've been infected with TB bacteria and treatment is important to prevent progression to active TB, especially if you have risk factors like HIV, diabetes, or are immunocompromised, as noted in the American Thoracic Society guidelines 1.
- Treatment completion is crucial even if you feel well, as the bacteria can remain dormant for years before potentially causing illness.
From the Research
Positive Quantiferon Test Over 10
- A positive Quantiferon test indicates the presence of latent tuberculosis infection (LTBI) 2, 3, 4.
- The test measures the release of interferon-gamma (IFN-gamma) in response to tuberculosis antigens, which is a specific indicator of LTBI 2.
- A positive result is typically defined as an IFN-gamma response above a certain threshold, usually 10 IU/ml 2.
Risk Factors for Positive Quantiferon Test
- Origin from a tuberculosis-endemic country is a significant risk factor for a positive Quantiferon test 2.
- Recent stay in a tuberculosis-endemic country, duration of tuberculosis exposure, and previous tuberculosis disease are also independently associated with a positive test result 2.
- Patients with immune-mediated inflammatory diseases (IMIDs) are at risk of reactivating LTBI, especially when treated with tumor necrosis factor-alpha (TNF-α) blocking agents 3.
Management of Positive Quantiferon Test
- The diagnosis of LTBI is indirect and relies on the detection of an immune response against tuberculosis antigens 4.
- There is currently no test for the direct identification of live Mycobacterium tuberculosis infection in humans 4.
- The World Health Organization (WHO) guidelines recommend using either a tuberculin skin test (TST) or an interferon-gamma release assay (IGRA) to detect LTBI in high-income and upper-middle-income countries 4.
- Early identification and treatment of individuals with LTBI is an important priority for tuberculosis control in specific groups at risk within the population 4.