The European Pharmacogenetics for AntiCoagulant Therapy project (EU-PACT; NCT01119300, https://clinicaltrials.gov/ct2/show/NCT01119300) included two single-blind, randomized trials that aimed to compare a genotype-guided dosing algorithm that included clinical variables and genotyping for CYP2C9 and VKORC1 with a dosing algorithm that included only clinical variables, for the initiation of warfarin, acenocoumarol or phenprocoumon treatment in patients with atrial fibrillation or venous thromboembolism [18, 19]. This evidence concerns the gene CYP2C9 and atrial fibrillation.