Genovesi and Carrero1 raise the important issue of achieving and maintaining optimal international normalized ratio (INR) control in patients with atrial fibrillation, a task that may be more challenging among those with chronic kidney disease (CKD). Given the importance of time in therapeutic range in determining the safety and effectiveness of warfarin,2 we agree that better understanding of the predictors of poor INR control and the implementation of risk-based management strategies based on this assessment could contribute to a favorable risk-benefit profile with warfarin therapy in patients with CKD with atrial fibrillation.