In a randomized controlled trial, the absolute risk in the treatment group is 10% and in the control group is 25%. What is the Number Needed to Treat (NNT)?
- A 4
- B 10
- C 7 ✓
- D 15
Correct answer: C. 7
Explanation
NNT = 1 / Absolute Risk Reduction. Absolute Risk Reduction = Control risk - Treatment risk = 25% - 10% = 15% = 0.15. NNT = 1/0.15 = 6.67, rounded to 7. The NNT indicates how many patients must be treated to prevent one additional adverse event compared to the control group.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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