A nurse is preparing to administer purified protein derivative (PPD) to a client. The nurse should use which of the following routes?

A. Subcutaneous: The subcutaneous route deposits medication into the fatty tissue beneath the skin. PPD testing requires a slow, localized immune reaction, which cannot be accurately assessed if administered subcutaneously, making this route inappropriate. B. Intramuscular: Intramuscular injections deliver medication into muscle tissue for systemic absorption. PPD relies on a localized delayed-type hypersensitivity reaction in the dermis, so IM administration would prevent accurate interpretation of the test. C. Intradermal: PPD is administered intradermally, usually on the inner forearm, to produce a small, raised wheal. This allows for proper exposure of immune cells in the dermis to the antigen, enabling assessment of induration 48–72 hours later and accurate detection of tuberculosis exposure. D. Oral: Oral administration does not provide a localized skin reaction necessary for PPD testing. The immune response required for interpreting the test cannot occur via the gastrointestinal route, making oral administration inappropriate.