Self-reported adherence to direct oral anticoagulants versus warfarin therapy in a specialized thrombosis service-a cross-sectional study of patients in a Canadian Health Region

Purpose: Direct oral anticoagulants (DOACs) have a better safety and efficacy profile than warfarin and are currently recommended for stroke prevention in non-valvular atrial fibrillation (AF) and treatment of venous thromboembolism (VTE). Given that DOACs do not require regular laboratory monitoring compared to warfarin, patients' interactions with the health care system is reduced. Adequate adherence to DOACs is important and reported adherence to anticoagulation is unclear in clinical practice. This study aims to assess self-reported adherence to oral anticoagulants in a specialized Adult Outpatient Thrombosis Service (TS).  METHODS: This cross-sectional study included patients aged ≥ 18 years who were prescribed an oral anticoagulant and had attended at least one appointment with an Adult Outpatient Thrombosis Service (TS) between October 10, 2017, and May 31, 2019. Adherence to oral anticoagulant therapy was assessed using the 12-item validated Adherence to Refills and Medications Scale (ARMS) score. Logistic regression analyses were used to evaluate association between patient characteristics and medication adherence. Adherence rates in DOACs and warfarin were compared.

Results: Three hundred and ninety-nine patients completed and returned the survey. Of the 399 who completed the survey, 74% were prescribed DOACs and 26% received warfarin. Most of the patients (89.3%) were ≥ 50 years of age and half (57.3%) were male. About two-thirds (67%) had at least post-secondary education. The duration of anticoagulation use differed between patients on DOAC and warfarin; a greater proportion of those who had used anticoagulants for less than 1 year was on DOACs compared to warfarin (20.9% vs 4.9%, p = 0.001). For patients who had been on anticoagulation for > 5 years, the proportion of warfarin patients was greater than DOAC (57.8% vs 20.5%, p = 0.001). Self-reported adherence to oral anticoagulant therapy using the 12-item ARMS scale for warfarin and DOACs were 87.3% and 90.9%, respectively. Among the warfarin users, patient satisfaction with TS was associated with medication adherence (OR = 0.22; 95% CI: 0.05-0.89).

Conclusions: Self-reported medication adherence was similar between warfarin and DOACs. Since suboptimal adherence is associated with poor clinical outcomes and increased costs, various stakeholders should emphasize the importance of medication adherence to oral anticoagulants at each patient encounter.