Predictors for INR-control in a well-managed warfarin treatment setting

Warfarin is well studied in patients with non-valvular atrial fibrillation (AF). It has low complication rates for patients achieving individual Time in Therapeutic Range (iTTR) > 70%. The risk scores SAMe-TT(2)R(2) and PROSPER are designed to predict future TTR, but are derived from a heterogeneous population with generally low iTTR. The aim of this study was to evaluate predictors for high and low iTTR in an AF population in Sweden, where there is a generally good anticoagulation control. A retrospective register study based on Swedish warfarin dosing system AuriculA, including 28,011 AF patients starting treatment during 1 January 2006 to 31 December 2011. Complications and risk factors were analysed and related to iTTR. Mean age was 73.7 (SD ± 9.5) years, with 42.0% women. Mean CHA(2)DS(2)-VASc score (SD) was 3.6 (± 1.7). For patients with iTTR < 60% there were over three times higher prevalence of excessive alcohol consumption than for patients with iTTR > 70% (3.7% vs. 1.1%). Previous stroke were more prevalent for patients with high than low iTTR (17.1% vs. 20.3%). Concomitant comorbidities were associated with increased risk of poor iTTR. In Swedish AF patients, excessive alcohol use is clearly associated with iTTR below 60%. Patients with previous stroke are more likely to get iTTR above 70%, unlike those with concomitant disorders who more often have poor anticoagulation control. The SAMe-TT(2)R(2)-score cannot be applied in Sweden. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11239-018-1765-4) contains supplementary material, which is available to authorized users.