Abstract P138: Quality Improvment Strategy for Better Control of Warfarin Anticoagulaton in Outpatients

Abstract

Introduction: Warfarin is currently the only effective oral anticoagulant for thromboembolic prophylaxis in patients at high risk for stroke or other thromboembolic complications. Maintaining a therapeutic level of anticoagulation as measured by the International Normalized Ratio (INR) can be challenging, due to genetic differences in drug metabolism, multiple drug interactions, and variations in dietary vitamin K intake. We designed a program to improve our ability to keep our patients' INR within the therapeutic range. Methods: We established a baseline degree of INR control in the fall of 2007, measuring the INR for 50 sequential patients who required warfarin therapy for at least one month for each of our 5 physicians; therapeutic range was 2-3 for most indications, or 2.5-3.5 for mechanical valves. We then instituted an INR improvement program, making certain our office gave directions for subsequent warfarin dosing and the next INR testing directly to the patient only; reviewing all drugs and potential interactions at each contact; reviewing potential dietary and alcohol consumption issues at each contact; and utilizing a standard dosing protocol for any dose changes. We reassessed the degree of INR control 6 months later and 18 months later in a similar cohort, measuring 50 sequential patients for each of our 5 physicians. Results: At our most recent survey, the average age of our patients was 73.7 and 43% (108 of 250) were female. The indication for anticoagulation was atrial fibrillation in 81.6% (204 of 250), mechanical heart valve in 11.2% (28 of 250), and other indications in 7.2% (18 of 250). The percentage of patients within their therapeutic range was 62.4% (156 of 250) at the baseline survey, 66.0% (165 of 250) at the second survey, and 65.6% (164 of 250) at the most recent survey, p=0.42 comparing first to second, p=0.45 comparing first to third, and p=0.92 comparing second to third, none significantly different. Conclusion: Achieving and maintaining a therapeutic INR with warfarin dosing even with an aggressive quality improvement program is a continuing therapeutic challenge. More effective management strategies or alternative anticoagulants which may be simpler to manage remain a high priority.