To the Editor Hernandez et al1 reported that dabigatran was associated with a higher incidence of major bleeding than warfarin, particularly in patients of African ancestry. However, the authors did not offer an explanation for this important clinical observation. We propose that high plasma creatine kinase (CK) levels, commonly seen in patients of African ancestry, can potentially have an effect on the direct thrombin inhibitor dabigatran, increasing bleeding risk.