The T-SPOT.TB test is a blood test used to screen for tuberculosis (TB) infection. It is an indirect test for Mycobacterium tuberculosis infection, meaning it looks for evidence of the body's immune response to the bacteria, rather than directly detecting the bacteria itself.
The test works by measuring the number of T cells in the blood that release interferon-gamma (IFN-g) in response to stimulation by specific TB antigens, ESAT-6 and CFP-10. These antigens are unique to Mycobacterium tuberculosis and are not found in other bacteria.
If a person is infected with TB, their immune system will have developed T cells that recognize these antigens. When these T cells are exposed to the antigens in the test, they will release IFN-g, which is then measured by the test.
The T-SPOT.TB test has several advantages over the traditional tuberculin skin test (TST), including:
- One-visit test: The T-SPOT.TB test can be performed in a single visit, whereas the TST requires two visits.
- Easier to interpret: The results of the T-SPOT.TB test are easier to interpret than those of the TST, which can be subjective and influenced by factors such as the size and location of the injection.
- Less prone to false-positive results: The T-SPOT.TB test is less likely to produce false-positive results than the TST, which can occur in people who have been vaccinated with the BCG vaccine.
The T-SPOT.TB test is a valuable tool for screening for TB infection, particularly in individuals who are at high risk for the disease. However, it is important to note that the test cannot distinguish between latent TB infection and active TB disease.
