Which statement is true about sensitivity and specificity?

• A. They depend on disease prevalence.
• B. They vary with the spectrum of disease in populations.
• C. They are reciprocal measures.
• D. They are intrinsic properties of the test and do not depend on disease prevalence.

Answer: (D)

Sensitivity and specificity are measures of a test’s ability to correctly identify true disease status: sensitivity is how well the test detects those with the disease, and specificity is how well it identifies those without the disease. These characteristics are determined by the test itself and the chosen threshold, not by how common the disease is in the population. In other words, they are intrinsic properties of the test.

Prevalence affects predictive values—the likelihood that a positive test actually means disease (positive predictive value) or that a negative test means no disease (negative predictive value)—because those values depend on how likely disease is in the group being tested. So even though a test’s sensitivity and specificity stay the same across populations with different disease frequencies (assuming the threshold and test conditions are unchanged), the real-world interpretation of a positive or negative result changes with prevalence.