If a wheal does not appear after PPD is injected, what is the recommended course of action and why?

If a wheal does not appear after PPD is injected, what is the recommended course of action and why?

• A. Re-inject in the same arm at a new site because a wheal was not achieved
• B. Do nothing and document a negative result
• C. Immediately inject the PPD into the opposite arm because the initial placement may have been too deep
• D. Recheck after 24 hours for any delayed wheal

Answer: (C)

The main point is that a tuberculin skin test relies on getting the PPD into the dermal layer to produce a wheal. When no wheal appears, it usually means the injection wasn’t placed intradermally—often it went too deep into subcutaneous tissue or the technique wasn’t right. To get a valid result, administer the PPD again at a different site on the opposite arm. This helps ensure the second injection is delivered correctly into the dermis and yields a reliable wheal if the test should be positive. Do not rely on a negative result without confirming proper technique, and avoid repeating on the same site which could reproduce the same error. Remember to read the reaction after 48–72 hours.

The main point is that a tuberculin skin test relies on getting the PPD into the dermal layer to produce a wheal. When no wheal appears, it usually means the injection wasn’t placed intradermally—often it went too deep into subcutaneous tissue or the technique wasn’t right. To get a valid result, administer the PPD again at a different site on the opposite arm. This helps ensure the second injection is delivered correctly into the dermis and yields a reliable wheal if the test should be positive. Do not rely on a negative result without confirming proper technique, and avoid repeating on the same site which could reproduce the same error. Remember to read the reaction after 48–72 hours.