TTR-INR guided warfarin adjustment protocol: A strategy to improve time in therapeutic range in patients with atrial fibrillation receiving warfarin

Background: Atrial fibrillation (AF) is a causing ischemic stroke. Warfarin remains a viable oral anticoagulant for many patients. Time in therapeutic range (TTR) is still not widely applied in clinical practice. Purpose: To study the association of change of TTR after implementation of TTR-INR guided warfarin adjustment protocol in patients with AF receiving warfarin. Methods: This is a prospective study of patients with AF at warfarin clinic of King Chulalongkorn Memorial Hospital. TTR was calculated by using Rosendaal linear interpolation method at baseline, 6 and 12 months after protocol implementation. Patient characteristics and outcomes (TTR improvement, embolic and bleeding events, and mortality) were collected. McNemar’s Chi-square test and paired t-test were used to evaluate the relationship between protocol implementation and outcomes. Results: A total of 57 patients were primary analyzed (mean age of 72 years, 50% females). The TTR at baseline was 65% (53% of patients had TTR less than 65%). After 12 months of protocol implementation, TTR were significantly improved (80%) (p<0.001). Significant improvement of proportion of patients with TTR ³65% was shown after protocol implementation (from 47% to 88%) (p<0.001). Three patients died during the follow-up. No ischemic or major bleeding events were occurred during the follow-up in the first 12 months. Conclusion: The TTR was significantly improved after 12 months of protocol implementation. This strategy may offer additional value in TTR improvement and good outcomes in patients with AF receiving warfarin.