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The quality of international normalised ratio control in southern Tasmania

To the Editor: The Australian Government’s recently completed Review of anticoagulation therapies in atrial fibrillation (AF) identified that the quality of international normalised ratio (INR) control was one of a number of factors creating uncertainty regarding the cost-effectiveness of novel anticoagulants in the Australian setting.1

INR control, usually expressed as the percentage of time in the therapeutic range (TTR), is critical in determining the relative efficacy, safety and cost-effectiveness of novel anticoagulants compared with warfarin.2,3 There is a strong correlation between TTR and clinical outcomes for patients taking warfarin.4,5 A review of retrospective studies in patients with AF found that a 7% improvement in TTR is associated with one less haemorrhagic event per 100 patient-years and a 12% improvement is associated with one less thromboembolic event per 100 patient-years.5

There is a paucity of data available regarding INR control…