There are two types of tests for TB infection: the TB skin test and the TB blood test. A person’s health care provider should choose which TB test to use.
The TB skin test is also called the Mantoux tuberculin skin test (TST). For this test, a small amount of fluid (tuberculin) is injected just below the top layers of skin on the lower part of the arm. Two to three days later a health care worker checks the arm to see if a bump has developed and measures the size of the bump. If the bump is of a certain size, the test is positive and the person has TB infection.
TB blood tests are also called interferon-gamma release assays or IGRAs. Two TB blood tests are approved by the U.S. Food and Drug Administration (FDA) and are available in the United States: the QuantiFERON®–TB Gold In-Tube test (QFT-GIT) and the T-SPOT®.TB test (T-Spot). For this test, a health care provider will draw blood and send it to a laboratory for analysis and results. If the test results are positive, the person has TB infection.
TB blood tests are preferred for persons who have received the TB vaccine bacille Calmette–Guérin (BCG).
If either the TB skin test or blood test is positive, additional tests are needed to determine if the person has TB disease. These tests include a chest x-ray and possibly testing of a person’s sputum (the material that is sometimes coughed up from the lungs).
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