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​​We offer an online course on how to properly do and read a TB Skin Test E Learning Module (30 minutes to complete). 

  • Best practice indicates that a two-step tuberculin skin test (TST) involves two tests performed within one to four weeks of each other. The second test can be completed up to one year from the first test, provided there hasn’t been an exposure to infectious tuberculosis (TB) disease during that time period. It cannot be done less than one week from the first test.
  • Why a Two-Step Test? : A single TST may elicit little response (a negative reaction) yet stimulate an anamnestic immune response. The second TST will elicit a much greater response (a positive reaction). This booster effect is important to detect, as it could be confused with a new TB infection.
  • When Should a Two-Step Test be Done?: A two-step TST should be performed if subsequent TSTs will be conducted in the future (e.g., among health care or correctional service workers). The two-step protocol needs to be performed once only if properly performed and documented. It never needs to be repeated. Any subsequent TST can be one step, regardless of how long it has been since the last TST.
  • If the first test in the two-step TST is positive, the second TST is not required. The individual should be medically evaluated with a chest x-ray and symptom review.

Person with unknown TST

  • A two-step test is required.
  • If both tests are negative, no further testing is required.
  • If either test is positive, refer to person with a positive TST.

One documented negative TST

  • ​If the TST was done in the past 12 months only a one-step TST is required.
  • If the result is positive, refer to person with a positive TST.

Properly documented results of previous two-step TST

  • If both tests are negative only a one-step test is required.
  • If the result is positive, refer to person with a positive TST.
  • If any previous test was positive, refer to person with a positive TST.

Person with a Positive TST

  • The person must have a medical assessment and chest x-ray.
  • Further skin testing isn’t recommended.
  • The person should be informed of the signs and symptoms of active TB disease.
  • Any person with symptoms of TB should not work until there is documentation from their health care provider that they do not have active TB disease.
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