Background

Use of oral anticoagulants such as warfarin is increasing. Part of the reason for this is the rising prevalence of atrial fibrillation, an ageing population and the widening indications for treatment based on evidence of benefit in reducing risk of stroke. A meta-analysis of 29 randomised trials including 28 044 participants with atrial fibrillation found that warfarin decreased the absolute risk of stroke by 2.7% per year (the number needed to treat (NNT) 37) compared with placebo or no treatment and by 0.7% per year (NNT=143) compared with aspirin.1

Management of warfarin, however, is challenging because of the considerable variability in warfarin’s action and the narrow ‘therapeutic range’, which requires frequent testing of international normalised ratio (INR) values and appropriate adjustment to prevent major complications. Often, poor control means that much of the potential benefit is not realised. Point-of-care devices, which allow self-testing of INR, with a drop of whole blood, are one of the options to optimise management by potentially reducing the need to attend anticoagulation clinics and offering the possibility for more continuous measurement.2 The first randomised trial of patient self-testing, published in 1989, included 50 patients on warfarin but with poorly controlled INRs, found that self-testing in the home setting provided accurate measurements, was feasible and achieved superior control compared with standard anticoagulation clinic care.3 Over time, there …