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Specificity — USMLE Step 3 MCQ

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EasyPreventive Medicine, Epidemiology, BiostatisticsSpecificityUSMLE Step 3

A screening test is compared with a gold standard. Among 200 patients without disease, 180 test negative and 20 test positive. Among 100 patients with disease, 85 test positive. Which of the following is the most likely explanation for this patient's findings?

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Correct answer: D — 90%

Specificity is the proportion without disease who test negative: 180/200 = 90%.

Reference: Users' Guides to the Medical Literature: Diagnostic Tests