An 86-year-old woman in whom nonvalvular atrial fibrillation has been detected. She has a CHADS2 score of 3 points. In the literature, similar patients on warfarin therapy have a stroke risk of 2.2% vs. 5.2% in patients without warfarin. What would be the number needed to treat (NNT) to prevent an emboligenic stroke with anticoagulation therapy:
On average, if 100 patients like this woman are treated with warfarin, the number of strokes is reduced by 3 (from 5.2 untreated to 3.2 treated). Therefore, if you treat 33.3 patients like this woman with warfarin, you reduce the number of strokes by 1: the NNT is 33.3.
3
19,2.
33,3.
49,5.
On average, if 100 patients like this woman are treated with warfarin, the number of strokes is reduced by 3 (from 5.2 untreated to 3.2 treated). Therefore, if you treat 33.3 patients like this woman with warfarin, you reduce the number of strokes by 1: the NNT is 33.3.