Incidence of severe renal dysfunction among individuals taking warfarin and implications for non–vitamin K oral anticoagulants

Background The purpose of this study is to assess incidence and risk factors for severe renal dysfunction in patients requiring oral anticoagulation to help guide initial drug choice and provide a rational basis for interval monitoring of renal function for patients prescribed non–vitamin K oral anticoagulants. Methods Patients on warfarin for atrial fibrillation or venous thromboembolism were consecutively enrolled from January 2007 to December 2010. Baseline kidney function was assessed, and patients were followed to their first decline of kidney function to creatinine clearance <30 mL/min. Multivariate regression assessed independent risk factors for the primary outcome. Severe renal impairment based on baseline kidney function was assessed by Kaplan-Meier analyses. Results Of 787 patients identified, 34 were excluded for baseline CrCl <30 mL/min. The mean age was 71 years, and 74% and 31% had hypertension and diabetes mellitus, respectively. At baseline, 23% (n = 174) had moderate chronic kidney disease (CKD) (CrCl 30-59 mL/min), whereas 31% had mild CKD (CrCl 60-89 mL/min). Severe renal impairment occurred in 92 patients (12%), 25% of which was seen within 5.3 months. Of those with baseline stage 3 CKD, 37% developed severe renal impairment. Stage 3 CKD conferred a 14-fold increased risk in the development of severe renal dysfunction (odds ratio 14.5, 95% CI 6.7-31.3, P < .001). Coronary artery disease was also associated with severe renal impairment (odds ratio 2.2, 95% CI 1.3-3.8, P = .004). Conclusions Acute and chronic renal dysfunction is common among individuals requiring long-term anticoagulant therapy. Patients with moderate chronic kidney disease and coronary artery disease are at the highest short-term risk of developing severe renal impairment. More frequent monitoring of these patients is warranted.