A clinical trial evaluates a new antihypertensive drug. The incidence of stroke in the treatment group is 3% and in the placebo group is 8% over 5 years. The Number Needed to Treat (NNT) to prevent one stroke is:
- A 5
- B 10
- C 20 ✓
- D 25
Correct answer: C. 20
Explanation
Absolute Risk Reduction (ARR) = Risk in control – Risk in treatment = 8% – 3% = 5% = 0.05. NNT = 1/ARR = 1/0.05 = 20. The NNT indicates that 20 patients need to be treated for 5 years to prevent one stroke; smaller NNT values indicate more effective interventions.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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