Quality of anticoagulation monitoring in nonvalvular atrial fibrillation patients: Comparison of anticoagulation clinic versus usual care

BACKGROUND: Prior research suggests that receiving specialized anticoagulation services enables patients to achieve better clinical outcomes. OBJECTIVE: To assess the quality of anticoagulation therapy in patients with atrial fibrillation who were enrolled in an anticoagulation clinic (ACC) versus usual care (UC). METHODS: Using Sharp Rees-Stealy physician group claims data, we estimated time spent in therapeutic range and time to first major bleeding episode or stroke for ACC and UC patients. t-Tests were used to compare time in therapeutic range proportions, and Kaplan-Meier survival analysis was performed to compare rates of bleeding and stroke between groups. RESULTS: We identified 1107 patients (351 ACC, 756 UC) treated with anticoagulation therapy for atrial fibrillation with more than one international normalized ratio (INR) reported between March 2001 and March 2004. ACC patients spent a greater proportion (68.14%) of time in therapeutic range compared with UC patients (42.07%; p < 0.001). There was a significant difference between groups in average time between INR tests (ACC = 14.31 days, UC 18.39 days; p < 0.001). ACC patients were 59% less likely to experience a bleed following the index date than were UC patients (HR = 0.41; 95% CI 0.2444 to 0.6999; p = 0.001), but type of care was not a significant predictor for stroke (HR = 0.95; 95% CI 0.5125 to 1.7777; p value NS). CONCLUSIONS: Results from this observational study reinforce the positive impact that anticoagulation services have on anticoagulation therapy outcomes, emphasizing the importance of providing such services for patients undergoing treatment with warfarin.