A clinical trial finds that 20% of patients in the treatment arm and 30% in the placebo arm develop the outcome. The Number Needed to Treat (NNT) to prevent one additional outcome is:
- A 10 ✓
- B 5
- C 15
- D 20
Correct answer: A. 10
Explanation
NNT = 1 / Absolute Risk Reduction (ARR). ARR = 30% − 20% = 10% = 0.10. NNT = 1 / 0.10 = 10. NNT is the reciprocal of ARR, not Relative Risk Reduction. Relative Risk Reduction = 10/30 = 33.3%, but NNT uses ARR.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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