Potential Factors Affecting the Anticoagulation Control in Patients Treated with Warfarin: Results WARFARIN-TR Study

Background: In the present study, we aimed to evaluate the factors that might be caused by adequate anticoagulation control in patients treated with warfarin for any reason. Methods: The WARFARIN-TR (The Awareness, Efficacy, Safety, and Time in Therapeutic Range of Warfarin in Turkish Population) study included 4987 patients using warfarin between January 1, 2014 and December 31, 2014. Time in therapeutic range (TTR) was calculated according to F. R. Roosendaal's algorithm with linear interpolation. The study population divided into two groups; adequate international normalized ratio (INR) control when TTR ≥70% (Group 1, n = 1068, 21.4%) and inadequate INR control when TTR <70% (Group 2, n = 3919, 78.6%). All demographic and clinic characteristics of the patients were compared to determine possible factors that might be cause adequate warfarin use. Results: The mean age of the study population was 60.7 ± 13.5 years, and there was no significant difference between groups. The mean TTR value of Group 1 was significantly higher than Group 2 (80 ± 8.5 vs. 40.9 ± 17.2; P < 0.001). The traditional cardiovascular risk factors were similar between groups except hypertension (Group 1 51.4% and Group 2 56.4%; P = 0.004) and chronic kidney disease (Group 1 8.3% and Group 2 5.5%; P = 0.001). There were no significant differences between groups regarding bleeding. The awareness of warfarin use was significantly higher in Group 1 patients than Group 2 patients. Multivariate logistic regression analysis revealed that age (odds ratio [OR], 1.007; P = 0.014), hypertension (OR, 0.821; P = 0.01), atrial fibrillation (OR, 1.180; P = 0.033), chronic kidney disease (OR, 1.697; P < 0.001), to know warfarin use reason (OR, 1.699; P < 0.001), and know to food-drug interaction with warfarin (OR, 1.583; P < 0.001) were independent predictors of adequate coagulation. Conclusion: Our study demonstrated that a low proportion of patients taking warfarin achieve an adequate TTR in daily practice. Furthermore, the patients with adequate TTR are more aware of warfarin use.