Estimated glomerular filtration rate is associated with major bleeding complications but not thromboembolic events, in anticoagulated patients taking warfarin

Abstract

Background: Decreased glomerular filtration rate is an established risk factor for bleeding but there are limited data on its association with bleeding risk in well-controlled anticoagulated patients taking warfarin.

Objectives: The aim was to investigate the relationship between glomerular filtration rate, major bleeding and thromboembolic complications in patients with tight anticoagulation control.

Patients/methods: A cohort study of patients from a Swedish quality register for anticoagulation, including all the registered patients that received anticoagulation during 2008 in the anticoagulation center of Skåne University Hospital, Malmö. Key outcome measures were major bleeding and arterial or venous thrombosis during 2008. A total of 3536 patients (2875 treatment years) were included.

Results: Total rates of 2.6 (2.0-3.2) bleeding events and 1.8 (1.3-2.3) thrombotic events per 100 treatment years were recorded (75 bleeding and 51 thromboembolic events). Data on estimated glomerular filtration rate were available in 3349 patients. Mean time in therapeutic range (international normalized ratio 2.0-3.0) was 74.5% (n=2894). Major bleeding events were significantly related to age and percentage of time with international normalized ratio >3.0 (P<0.001). Glomerular filtration rate levels <30 ml/min/1.73 m(2) were particularly associated with high risk of bleeding, especially in elderly patients. No correlation between glomerular filtration rate and thromboembolic events was seen.

Conclusions: With good anticoagulation control as measured by time in therapeutic range, patients had a relatively low risk for major bleeding if their renal function is normal. Despite good anticoagulation control, severely impaired kidney function is associated with a very high yearly risk of major bleeding events.