There are two types of tests for TB infection, skin tests and blood tests. In TB skin tests, a small amount of fluid known as tuberculin is injected beneath the skin. In 48-72 hours, the patient returns to the health care provider to have the health care provider look for a reaction at the site of the injection. The skin test is also known as a tuberculin skin test or Mantoux test. A positive result means the person was infected with TB bacteria at some point. It does not tell if the infection is currently active.
The TB blood test is known as an interferon-gamma release assay. 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 Plus (QFT-Plus) and the T-SPOT®.TB test (T-Spot). A positive test means the person has been infected with TB bacteria. It also does not prove whether or not the infection is currently active.