Quality of warfarin management following transfer from an anticoagulation clinic to primary care

BACKGROUND: Advances in alternative oral anticoagulants has reduced use and clinician comfort with warfarin. Our specialty anticoagulation clinic (AC) operates at maximum capacity and must transfer patients to accept new referrals. OBJECTIVES: To compare time within therapeutic range (TTR) during 6 months of AC care versus following transfer to primary care for a minimum of 6 months and to a maximum of 24 months. Secondarily, to compare frequency of INR assessments, proportion of INRs ≤1.5 and > 5, and rates of bleeding and thromboembolic events post-transfer to primary care. METHODS: Mixed retrospective chart review and administrative audit with a before-after study design for patients managed by the University of Alberta's AC for at least 6 months that were transferred to primary care. RESULTS: 177 (27.7 %) patients were included, managed by the AC for 3.4 years (1.3, 7.9). TTR declined during the first 6 months post-transfer with AC care achieving 69.2 % and primary care 64.5 % (p = 0.02) and when compared to the 24-month interval (69.2 % vs 63.4 %; respectively; p = 0.003). A shorter interval between INRs in AC care was observed (28.9 (24.4) vs 34.5 (31.7) days, respectively; p = 0.0004). Similar numbers of critical INRs occurred between groups, whereas more INRs ≤1.5 occurred in primary care (7.3 % vs 4.7 %, respectively; p = 0.0003). Bleeding and thromboembolic event rates were balanced following transfer to primary care with both occurring at 9.4 % per patient year. CONCLUSION: A decline in anticoagulation control after transfer to primary care was observed, which appeared to be driven by a greater proportion of subtherapeutic INRs.