Demand for warfarin anticoagulation monitoring in Tayside, Scotland

Aim: The aim of this study was to assess the demand for warfarin prescribing and monitoring, and to identify patients with atrial fibrillation who might benefit from warfarin therapy. The study was carried out in the population of Tayside, Scotland (400,000 people) using patient-specific dispensed prescribing and hospitalisation data from the Medicines Monitoring Unit at the University of Dundee.

Methods: The incidence and prevalence of digoxin and warfarin prescribing were calculated between 1989 and 1993. Patients dispensed digoxin in 1993 were assumed to have atrial fibrillation and they were stratified into high risk groups for an adverse thromboembolic event based on past medical history. The numbers of patients at high risk who were judged to be possible candidates for warfarin were calculated.

Results: The prevalence of warfarin prescribing is increasing in Tayside and is mainly for elderly patients. There were also many patients assumed to have atrial fibrillation who were at particularly high risk for an adverse thromboembolic event, who had no record of warfarin prescribing. Only 35% received warfarin. Even given the methodological limitations of this study, and the use of aspirin as an alternative prophylactic agent, it is likely that these patients have been a source of increased prevalence of warfarin prescribing since 1993 and will be in the future. Other indications for warfarin prescribing are also increasing.

Conclusion: It is anticipated that there will be increasing demands for anticoagulant monitoring, which will need to be met either by increasing the capacity of existing clinics, or by increasing the role of primary care.