Q. A trial assessed a statin tablet compared to placebo for stroke prevention over 1 year. There were 10% of patients developing stroke in the group taking a tablet and 20% in the carotid endarterectomy group developing a stroke over the 1 year. What is the number needed to treat over 1 year to prevent 1 death? Options: A. 1 B. 10 C. 10 0 D. 1000 Answer: B. 10 Explanation: Number needed to treat (NNT) is defined as number of patients being given treatment for prevention of one death. Number need to treat: 1/Absolute risk reduction Stroke in patients taking tablet: 10%= 0.1 Stroke in patients undergoing endarterectomy: 20%= 0.2 Absolute risk reduction: 0.2-0.1= 0.1 So, Number needed to treat to save one life: 1/0.1= 10