The two algorithms are Square root of Warfarin maintenance dose (mg/day)  = 1.68143 – 0.0029*age +0.30784*BSA – 0.2633*(VKORC1 g.3588G>A) – 0.19114*(CYP2C9*3) +0.14735*(CYP4F2 c.1297G>A) – 0.1797*amiodarone – 0.4138*fluconazole – 0.1888*diltiazem and Square root of Warfarin maintenance dose (mg/day)  = 2.140-0.370*(VKORC1-1639 G>A) – 0.332* (CYP2C9*3) +0.324 *BSA -0.004*age-0.231*(number of increasing INR drugs) +0.105*(smoking habit) -0.135*(preoperative stroke history) – 0.108* (hypertension), respectively. This evidence concerns the gene CYP2C9 and Stroke.