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Absolute risk reduction and NNT — USMLE Step 3 MCQ

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EasyPreventive Medicine, Epidemiology, BiostatisticsAbsolute risk reduction and NNTUSMLE Step 3

A randomized trial reports that a new antihypertensive drug reduced stroke from 4% to 3% over 5 years. The p value is 0.03 and the trial had complete follow-up. A patient asks how many people need treatment 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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Correct answer: E — Absolute risk reduction of 1%

The absolute risk reduction is 4% minus 3%, or 1%. The number needed to treat is the reciprocal of the absolute risk reduction: 1/0.01 = 100.

Reference: USMLE Step 3 biostatistics content outline