Evaluation of time in therapeutic range in anticoagulated patients: a single-center, retrospective, observational study

BACKGROUND: The percentage of time during which the patients have the INR within the target values (i.e. Time in Therapeutic Range [TTR]) is a measure of anticoagulation quality with Vitamin K Antagonists (VKA). To evaluate the quality of anticoagulation using TTR according to the Rosendaal method, we performed an observational, retrospective study. We included all outpatients who attended the cardiology anticoagulation clinic of a Portuguese hospital (2011-2013), whose target INR was 2.0-3.0. RESULTS: 377 VKA-treated patients were evaluated. Of these, 72.4% had non-valvular atrial fibrillation. Patients were followed for a mean period of 471 days. The mean TTR was 60.3% (SD 19.3%) and 44.3% of the patients had a mean TTR<60%. Patients were at high risk of bleeding (INR>4.5) and at high thrombotic risk (INR<1.5) during, respectively, 1.7% and 4.7% of the time. CONCLUSIONS: Anticoagulation control needs to be improved. These results are informative for all stakeholders: patients, health care professionals, and policymakers.