Which route is commonly used for tuberculosis skin testing?

Which route is commonly used for tuberculosis skin testing?

• A. Intradermal
• B. Oral route
• C. Rectal route
• D. Intramuscular

Answer: (A)

Tuberculosis skin testing relies on injecting the antigen into the skin, not into muscle or other tissues, so the immune system in the skin can produce a localized delayed-type hypersensitivity reaction. An intradermal injection of purified protein derivative is placed in the dermis to create a small, visible wheal. After about 48 to 72 hours, the clinician checks for induration—a firm, raised area—rather than just redness. This intradermal placement is essential because it exposes immune cells in the skin to the antigen, allowing sensitized T cells to respond and produce a measurable reaction. Delivering the substance by an oral, rectal, or intramuscular route would not generate the same skin-specific response, so those routes are not used for TB skin testing.

Tuberculosis skin testing relies on injecting the antigen into the skin, not into muscle or other tissues, so the immune system in the skin can produce a localized delayed-type hypersensitivity reaction. An intradermal injection of purified protein derivative is placed in the dermis to create a small, visible wheal. After about 48 to 72 hours, the clinician checks for induration—a firm, raised area—rather than just redness. This intradermal placement is essential because it exposes immune cells in the skin to the antigen, allowing sensitized T cells to respond and produce a measurable reaction. Delivering the substance by an oral, rectal, or intramuscular route would not generate the same skin-specific response, so those routes are not used for TB skin testing.