OA Epidemiology

Balancing Individual Benefits and Risks of Warfarin in Patients with Atrial Fibrillation

Proceedings of the 2013 annual meeting of the Netherlands Epidemiology Society

Volume 1 Issue S1 Abstract 31


H.A. van den Ham, Utrecht University, Utrecht, the Netherlands
O.H. Klungel, Utrecht University, Utrecht, the Netherlands
H.G.M. Leufkens, Utrecht University, Utrecht, the Netherlands
T.P. van Staa, Utrecht University, Utrecht, the Netherlands; Medicines and Healthcare Products Regulatory Agency, London, UK

Anticoagulation with warfarin reduces the risk of ischaemic stroke in patients with atrial fibrillation (AF). Benefit-risk balance is positive in the overall population, but hardly studied on an individual level. The aim was to estimate benefits and risks of warfarin treatment for the individual and identify characteristics determining the benefit-risk balance.

The cohort consisted of patients with AF exposed to warfarin in the Clinical Practice Research Datalink (CPRD). Outcomes of interest were ischaemic stroke, transient ischaemic attack, haemorrhagic stroke and major bleed. The probability of an outcome during exposure was estimated and attributable risks for each outcome were estimated using the relative rates of warfarin effects. The individual net benefit was calculated as the weighted sum of benefits minus adverse effects and then characterized as being less favourable (net benefit <0.5), neutral (net benefit 0.5-1.5) or favourable (net benefit >1.5). Logistic regression was used to identify characteristics that explained a less favourable  net benefit compared to a favourable net benefit.

The study population included 33,772 patients with AF exposed to warfarin. Characteristics associated with a less favourable benefit-risk balance were presence of congestive heart failure  (OR 2.67, 2.27-3.14),  cancer (OR 2.51, 2.19-2.88),  minor  bleed (OR 2.68, 2.25-3.18) and renal insufficiency (OR 3.30, 2.37-4.60).  Presence of hypertension (OR 0.41, 0.36-0.46) and vascular disease (OR 0.16, 0.13-0.19)  were protective.

We confirmed that the net benefit of warfarin for the overall  AF population is positive. However, there is a large variation of benefit-risk balance across this population for individual patients.

Published: 06 Jun, 2013

Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)