Warfarin utilisation and anticoagulation control in patients with atrial fibrillation and chronic kidney disease.

Objective To evaluate warfarin prescription, quality of international normalised ratio (INR) monitoring and of INR control in patients with atrial fibrillation (AF) and chronic kidney disease (CKD). Methods We performed a retrospective cohort study of patients with newly diagnosed AF in the Veterans Administration (VA) healthcare system. We evaluated anticoagulation prescription, INR monitoring intensity and time in and outside INR therapeutic range (TTR) stratified by CKD. Results Of 123 188 patients with newly diagnosed AF, use of warfarin decreased with increasing severity of CKD (57.2%-46.4%), although it was higher among patients on dialysis (62.3%). Although INR monitoring intensity was similar across CKD strata, the proportion with TTR >= 60% decreased with CKD severity, with only 21% of patients on dialysis achieving TTR >= 60%. After multivariate adjustment, the magnitude of TTR reduction increased with CKD severity. Patients on dialysis had the highest time markedly out of range with INR < 1.5 or > 3.5 (30%); 12% of INR time was > 3.5, and low TTR persisted for up to 3 years. Conclusions There is a wide variation in anticoagulation prescription based on CKD severity. Patients with moderate-to-severe CKD, including dialysis, have substantially reduced TTR, despite comparable INR monitoring intensity. These findings have implications for more intensive warfarin management strategies in CKD or alternative therapies such as direct oral anticoagulants.