Should we repeat a negative first PPD test in low risk individuals? - USMLE Forums
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Old 05-14-2012
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Lungs Should we repeat a negative first PPD test in low risk individuals?

In normal individual who are at no risk of TB, if they undergo PPD test (e.g. pre-work check up) and it return back normal, shall we consider this result conclusive or we should repeat the PPD to avoid booster phenomenon before clearing the individual.
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Old 05-14-2012
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i think the first PPD test u get done on anyone u hv to do twice.

subsequent tests are dont just once.
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Old 05-14-2012
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so for the exam purpose should i repeat or clear
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Old 05-16-2012
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Quote:
Originally Posted by bisho View Post
in normal individual who are at no risk of TB, if they undergo PPD test (e.g. pre-work check up) and it return back normal, shall we consider this result conclusive or we should repeat the PPD to avoid booster phenomenon before clearing the individual
A negative PPD rules out TB. You never repeat a PPD, period ! since the PPD itself sensitizes the person.
If in doubt do a QFT and assess it the results with other findings & tests like CXR.
Culture is the gold standard.

More here
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Old 05-16-2012
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Quote:
Originally Posted by Novobiocin View Post
A negative PPD rules out TB. You never repeat a PPD, period ! since the PPD itself sensitizes the person.
If in doubt do a QFT and assess it the results with other findings & tests like CXR.
Culture is the gold standard.

More here
So first time Neg --> rule out in low risk. Ok

but what about the booster phenomenon (when should we think of)?
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Old 05-16-2012
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Quote:
Originally Posted by bisho View Post
So first time Neg --> rule out in low risk. Ok

but what about the booster phenomenon (when should we think of)?
According to CDC

Quote:
Booster Phenomenon
Some people infected with M. tuberculosis may have a negative reaction to the TST if many years have passed since they became infected. They may have a positive reaction to a subsequent TST because the initial test stimulates their ability to react to the test. This is commonly referred to as the “booster effect” and may incorrectly be interpreted as a skin test conversion (going from negative to positive). For this reason, the “two-step method” is recommended at the time of initial testing for individuals who may be tested periodically (e.g., health care workers). If the first TST result in the two-step baseline testing is positive, consider that the person is infected and evaluate and treat the person accordingly. If the first test result is negative, the TST should be repeated in 1–3 weeks. If the second test result is positive, consider that the person is infected and evaluate and treat the person accordingly; if both steps are negative, consider the person uninfected and classify the TST as negative at baseline testing (see Figure 1).

When IGRAs are used for serial testing, there is no need for a second test because boosting does not occur.
Algorithm
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Infectious-Diseases, Preventive-Medicine-, Pulmonology-

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