What Does a Positive TB Skin Test or Blood Test Look Like?

Learn how to identify a positive TB skin or blood test result, including signs, timing, and factors affecting the test interpretation.

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A positive TB skin test or TB blood test generally means that the person has been infected with the TB bacteria. In a skin test, this is indicated by a swollen bump at the injection site, usually appearing within 48 to 72 hours after the test. For a positive result, the size of the bump varies depending on the person’s risk factors and medical background. In a TB blood test, a positive result means that the person's blood has reacted to the test, indicating a TB infection.

FAQs & Answers

  1. How soon after the TB skin test does a positive bump appear? A positive bump typically appears within 48 to 72 hours after the TB skin test injection.
  2. What does a positive TB blood test indicate? A positive TB blood test means that the blood cells have reacted to TB bacteria, indicating a TB infection.
  3. Does the size of the TB skin test bump vary for everyone? Yes, the size of the bump considered positive varies depending on the person's risk factors and medical history.

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