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Number needed to treat — USMLE Step 3 MCQ

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ModeratePreventive Medicine, Epidemiology, BiostatisticsNumber needed to treatUSMLE Step 3

A randomized trial of a new antihypertensive drug reports stroke in 2% of treated patients and 6% of placebo patients over 5 years. Mortality and adverse events are similar. A resident asks how many patients must be treated for 5 years to prevent one stroke. Which of the following is the most likely explanation for this patient's findings?

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Reveal the answer and explanation

Correct answer: B — 25

Absolute risk reduction is 6% minus 2% = 4%; number needed to treat is 1/0.04 = 25.

Reference: Users' Guides to the Medical Literature: Therapy