There are two common tests for tuberculosis:
Skin test: This is also known as the Mantoux tuberculin skin test. A technician injects a small amount of fluid into the skin of your lower arm. After 2 or 3 days, they’ll check for swelling in your arm.
If your results are positive, you probably have TB bacteria. But you could also get a false positive. If you’ve gotten a tuberculosis vaccine called bacillus Calmette-Guerin (BCG), the test could say that you have TB when you really don’t. The results can also be false negative, saying that you don’t have TB when you really do, if you have a very new infection. You might get this test more than once.
Blood test: These tests, also called interferon-gamma release assays (IGRAs), measure the response when TB proteins are mixed with a small amount of your blood.
Those tests don’t tell you if your infection is latent or active. If you get a positive skin or blood test, your doctor will learn which type you have with:
• A chest X-ray or CT scan to look for changes in your lungs
• Acid-fast bacillus (AFB) tests for TB bacteria in your sputum, the mucus that comes up when you cough
Courtesy: WebMD
