Key result
Dedicated anticoagulant clinics linked to ~82% TTR in AF patients versus routine care.
Why the study?
There is limited real-world data on the adequacy of warfarin control and the cost and burden of monitoring warfarin therapy in Canadian patients with non-valvular atrial fibrillation.
Observational (n=551)
Yes
In a real-world Canadian cohort of NVAF patients, long-term warfarin therapy achieved excellent overall time in therapeutic range (74.4%) with minimal impact on quality of life or work productivity, particularly when managed in dedicated anticoagulant clinics.
Clinic-based warfarin monitoring was associated with higher TTR in NVAF; extends real-world Canadian data but leaves outcome benefits open.
BACKGROUND: Despite the fact that direct oral anticoagulants (DOACs) are favoured over warfarin for stroke prevention in patients with non-valvular atrial fibrillation (NVAF), physicians need to maintain competence in using and monitoring warfarin since many patients have contraindications or other barriers to using DOACs. Unlike DOACs, warfarin therapy requires regular blood testing to ensure that it is within a target range to ensure efficacy and safety. There is limited real-world data on the adequacy of warfarin control and the cost and burden of monitoring warfarin therapy in Canadian NVAF patients. OBJECTIVES: In a large cohort of Canadian patients with NVAF on warfarin we assessed time in therapeutic range (TTR), determinants of TTR, process of care, direct costs, health related quality of life and loss of work time and productivity related to warfarin therapy. METHODS: Five hundred and fifty one patients with NVAF, either newly initiated or stable on warfarin were prospectively enrolled across 9 Canadian provinces from primary care practices and anticoagulant clinics. Participating physicians provided baseline demographic and medical information. Patients completed diaries for 48 weeks, capturing information about International Normalized Ratio (INR) test results, test locations, process of INR monitoring, direct costs of travel, health-related quality of life and work productivity measures. TTR was estimated using linear interpolation of INR results and linear regression used to investigate associations between TTR and factors (defined a priori). RESULTS: Four hundred and eighty (87.1%) patients had complete follow-up with an overall TTR of 74.4% based on 7,175 physician-reported INR values from 501 patients. 88% of this cohort were monitored through routine medical care (RMC). The average number of INRs per patient during the 48-week period was 14.1 (standard deviation (SD) = 8.3) tests with a mean duration of 23.8 (SD = 11.1) days between tests. We did not find a relationship between TTR and age, sex, presence of major comorbidities, patient's province of residence or rural vs. urban residence. 12% of patients monitored through anticoagulant clinics had significantly better TTR than patients monitored through RMC (82% vs. 74%; 95% confidence interval: -13.8, -1.2; p = 0.02). Health related quality of life utility values were high and remained consistent throughout the study. The majority of patients reported no impact on either work productivity or impairment of regular activities due to being on long-term warfarin treatment. CONCLUSIONS: We showed excellent overall TTR in an observed Canadian cohort, with monitoring through a dedicated anticoagulant clinic being associated with a statistically and clinically significant improvement in TTR. The burden of warfarin therapy on patients' health related quality of life or daily work and activities was low.
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Selby et al. (2023) conducted an observational in Non-valvular atrial fibrillation (n=551). Warfarin was evaluated on Overall Time in Therapeutic Range (TTR). Long-term warfarin therapy in Canadian patients with non-valvular atrial fibrillation achieved an overall time in therapeutic range of 74.4%, with monitoring through dedicated anticoagulant clinics significantly improving control compared to routine medical care (82% vs. 74%, p=0.02).