A TB skin test, also known as the Mantoux test, is performed by injecting a small amount of tuberculin (PPD) under the skin of your forearm.
The Process Explained
Here is a breakdown of the process, incorporating information from our reference:
- Injection: A healthcare professional injects 0.1 ml of tuberculin (PPD) intradermally into the inner surface of your forearm, using a needle and syringe. (Reference 1)
- Observation Period: The skin reaction is read 48 to 72 hours after the injection. (Reference 1)
- Reading the Results: The test result is based on measuring the raised, hardened area or swelling (induration) at the injection site in millimeters. (Reference 2)
What is Induration?
- Induration is the palpable (can be felt), raised, hardened area of swelling at the injection site. This is the key to interpreting the skin test.
- The size of the induration determines if the test is positive, negative, or requires further evaluation.
- Redness or swelling without induration is not considered a positive result.
Key Aspects to Remember
- Timing: The results must be read within the specified window of 48-72 hours.
- Measurement: Only the induration is measured, not redness.
- Healthcare Professional: This test needs to be performed and interpreted by a trained healthcare professional.
