A nurse is concerned about the accuracy of the purified protein derivative (tuberculin) test in screening individuals with tuberculosis exposure for followup chest radiography. The nurse's concern is related to which aspect of the test's validity?

• A. Reliability.
• B. Sensitivity.
• C. Specificity.
• D. Variability.

Answer: (B)

Sensitivity is about how well a screening test identifies people who truly have the condition. With the tuberculin skin test, a negative result can occur even in someone who has TB infection (false negative), especially if exposure is recent, immune function is compromised, or other factors affect skin reactivity. Since the next step is chest radiography to look for active disease, missing true infections means missing cases that should be investigated further. Therefore, the nurse’s concern about accuracy in this screening sequence centers on sensitivity—the test’s ability to detect those who actually have TB infection.