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Why Two Step Ppd?

Sarah Jenkins • • 7 min read
Why Two Step Ppd?

If the Mantoux tuberculin skin test (TST) is used to test health care personnel upon hire (preplacement), two-step testing should be used. This is because some people with latent TB infection

latent TB infection
What is Latent TB Infection? Persons with latent TB infection do not feel sick and do not have any symptoms. They are infected with M. tuberculosis, but do not have TB disease. The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood test.
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have a negative reaction when tested years after being infected. The first TST may stimulate or boost a reaction.

When do you give 2nd step PPD?

To avoid misinterpretation between a boosted response and a new infection, many facilities employ the 2-step procedure. In this procedure a person is given a baseline PPD test. If the test is (-), a second test is administered 1- 3 weeks later (i.e. the second test can be read 7-21 days after the first).

What is the difference between a 1 step and 2 step TB test?

The difference between a one-step and a two-step ppd is that the one step includes having the test administered and then read in 48-72 hours. If a two-step is necessary, you will need to return no earlier than 7 days after having the first test administered and repeat the same process (administration and read) again.

Sarah Jenkins
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Sarah Jenkins

Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.