Tuberculosis Blood TestDetect tuberculosis bacteria in the body. This test is for those who have been exposed to tuberculosis bacteria (Mycobacterium tuberculosis); require evidence of a negative tuberculosis test; or are at high risk for contracting tuberculosis. Read more
This test is an Interferon-Gamma Release Assays (IGRAs) whole-blood test that detects the immune system’s response to M. tuberculosis. M. tuberculosis, or TB bacteria, usually attack the lungs. However, TB bacteria can attack any part of the body such as the spine, kidneys, and brain. In fact, not everyone that becomes infected with TB bacteria will become sick. As a result, two TB-related conditions exist: latent TB infection (LTBI) and TB disease. If not treated properly, TB disease can be fatal. This test does not differentiate between latent tuberculosis infection (LTBI) and active TB disease.
LTBI is a carrier state of TB that can last for weeks, months, or years before developing into TB disease. Active TB is when tuberculosis bacteria overwhelm a person's immune system, and symptoms start to appear. The Tuberculosis Blood Test helps detect the presence of M. tuberculosis and can be a first step in the process of determining is someone has latent TB infection or TB disease. Further testing may be required if the blood test is positive.
How it works
- The results are either positive or negative, and have a lower risk of reader bias when compared to a skin test
- Accuracy is not affected by a prior bacillus Calmette-Guérin (BCG) TB vaccination
- Only requires a single patient visit (2 to 4 are required for the TST)
Live-virus vaccines may affect IGRA test results. However, the effect of live-virus vaccination on IGRAs has not been studied. Until more information is available, the CDC recommends that IGRA testing for live-virus vaccinations are performed as follows:
- Either on the same day as a live-virus vaccination or 4 to 6 weeks after the administration of a live-virus vaccination
- At least 1 month after a smallpox vaccination
You should not delay a COVID-19 vaccination due to testing for TB. The COVID-19 vaccine is not a live-virus vaccine. It does not affect the results of the TB blood test.