When performing a purified protein derivative (PPD) test for TB, which method is correct?

• A. Ensure the wheel forms
• B. Point the bevel of the needle downward
• C. Massage the area after the injection
• D. Use a 22 gauge, one-inch needle

Answer: (A)

Intradermal TB testing relies on placing a tiny amount of antigen into the superficial skin layer so a small wheal forms at the injection site. That wheal confirms the antigen is in the dermis and the test can be read reliably later. So the best action is to ensure a wheal develops after the injection.

Bevel orientation matters because intradermal injections are done with the bevel up to keep the needle tip in the superficial dermis and produce the characteristic wheal; pointing the bevel downward risks deeper injection and a poor wheal formation. Massaging the area after injection is avoided because rubbing can spread the antigen and alter the response, potentially skewing results. Regarding needle size, intradermal TB testing uses a small-gauge, short needle; a 22-gauge, one-inch needle is larger than what’s typical and could cause deeper tissue penetration and improper administration.