A retrospective study on the risk factors for bleeding events in warfarin therapy, focusing on renal function

Purpose The anticoagulant effect of warfarin used to treat stroke has been shown to vary with the concomitant use of medications and comorbidity. Concomitant use of antithrombotic drugs and underlying chronic kidney disease (CKD) represent risk factors for bleeding events. We conducted a comprehensive investigation of the background characteristics and concomitant use of drugs to identify the risk factors for warfarin-related bleeding, focusing on renal function. Methods The study population consisted of patients prescribed warfarin at the Tokyo Women’s Medical University Hospital. A retrospective review of the patient data, including bleeding events, bleeding sites, the patient’s background, concomitant use of drugs, and laboratory data was carried out, and the incidence of bleeding events was compared in patient groups stratified according to CKD stage and antithrombotic drug use. Multivariate logistic regression analysis was performed to determine the risk factors for warfarin-related bleeding. Results Of the 3,831 patients included in the study, the incidence of warfarin-related bleeding was 3.0 events per 100 patient-years. The multivariate logistic regression analysis identified age > 65 years, body mass index (BMI), alanine aminotransferase (ALT), estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m 2 , prothrombin time-international normalized ratio (PT-INR), and concomitant use of antithrombotic drugs as risk factors for warfarin-related bleeding. Conclusions The present analyses identified age > 65 years, BMI, ALT, eGFR <30 mL/min/1.73 m 2 , PT-INR, and concomitant use of antithrombotic drugs as independent risk factors for warfarin-related bleeding. We should pay attention to the risk factors associated with warfarin-related bleeding when prescribing warfarin in patients with renal impairment.