Advanced Patient Assessment 2025 – 400 Free Practice Questions to Pass the Exam

The skin test using purified protein derivative (PPD) is a diagnostic tool specifically designed to identify exposure to the bacterium responsible for tuberculosis (TB). When a PPD test is administered, the individual’s immune response to the injected proteins is measured after 48 to 72 hours. A positive reaction indicates that the person has been exposed to the bacteria, although it does not confirm active TB, necessitating further evaluation.

The specificity of the PPD test to tuberculosis lies in the fact that it is based on the body's immune response to mycobacterial antigens found in Mycobacterium tuberculosis. Individuals who have been infected with this bacterium develop delayed-type hypersensitivity reactions to the PPD, making it a reliable tool in screening for prior exposure to TB.

While the other options, such as histoplasmosis, coccidioidomycosis, and sarcoidosis, involve other types of fungal infections and immunological conditions, they do not utilize the PPD test for diagnosis. Each of these entities has its own diagnostic procedures and tests, which are not related to the PPD test used specifically for tuberculosis identification.