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Predictive value — USMLE Step 3 MCQ

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HardPreventive Medicine, Epidemiology, BiostatisticsPredictive valueUSMLE Step 3

A diagnostic test has the same sensitivity and specificity in two populations. Disease prevalence is higher in population A, and a positive result is more often a true positive there. Which measure is higher in population A?

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Correct answer: B — Positive predictive value, the probability of disease after a positive test

With unchanged sensitivity, specificity, and likelihood ratios, a higher pretest prevalence raises the positive predictive value. It does not alter the intrinsic sensitivity or specificity of the test.

Reference: CDC, Principles of Epidemiology in Public Health Practice: https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html