Variation in warfarin prescribing and dosing in the UK: a national survey of anticoagulation clinics

WHAT IS KNOWN AND OBJECTIVE: Clinical practice in the initiation, prescribing, dosing and monitoring of warfarin in the UK varies, but this has not been adequately documented. The objective was to undertake a survey on current clinical practice in this area, and how it compares with national guidelines that have been developed by the British Committee for Standards in Haematology. METHODS: A national online survey of anticoagulation clinics was performed using Survey Monkey(®) . The survey was designed to capture data for prescribing, dosing and monitoring of anticoagulation with warfarin. RESULTS: Of 85 clinics who responded to the survey, most were run by secondary care (68%), facilitated by specialist nurses (58%) and followed standard guidelines for the management of warfarin (87%). The majority of clinics indicated their target international normalized ratio (INR) for patients with atrial fibrillation (AF) (69/73; 94·5%) was between 2·0 and 3·0, but the indicated target INR for mechanical heart valves was more variable. Initiation and loading dosing regimens were a major source of variability with uncertainty surrounding individual patient factors such as age, ethnicity and BMI. WHAT IS NEW AND CONCLUSIONS: Current practice amongst UK anticoagulation clinics largely follows current national guidelines but better guidance on dosing, taking into account factors that determine interindividual variability in daily warfarin dose requirements would improve and standardize oral anticoagulation with warfarin.