What action should prompt a charge nurse to intervene while observing a nurse performing a Mantoux tuberculin skin test?

The appropriate action that should prompt a charge nurse to intervene is the improper handling of the injection site after administering the Mantoux tuberculin skin test. The correct procedure involves injecting the purified protein derivative (PPD) intradermally and not manipulating the site post-injection by massaging it. Massage can disperse the antigen beyond the test site, leading to an inaccurate reading and potentially causing localized irritation or an adverse reaction.

The other options reflect appropriate practices in the context of the Mantoux test. Documenting the results immediately ensures the patient’s record is current and allows for timely follow-up. Using sterile technique throughout the procedure is critical to prevent any risk of infection. Administering a pain reliever before the test may be considered appropriate for patient comfort, depending on the facilities' policies and the individual patient's needs. However, the main concern in the context of the skin test is the need to avoid manipulating the site post-injection.