Tuberculosis testing

Tuberculosis (TB) testing identifies if someone has been exposed to the bacteria that cause TB. The most common test is the skin test, where a small amount of fluid (tuberculin) is injected under the skin on the forearm. After 48-72 hours, a healthcare provider checks for a raised bump, which may indicate TB exposure. Alternatively, blood tests can measure the immune response to TB bacteria. These tests do not determine if someone has active TB disease, only if they have been exposed or infected previously. Further evaluation is needed if initial tests are positive.