Abstract Number: PB0203
Meeting: ISTH 2020 Congress
Theme: Coagulation and Natural Anticoagulants » Coagulation Factors and Inhibitors
Background: While warfarin treatment is continuously monitored by regular INR measurements, direct oral anticoagulant (DOAC) treatment is not controlled by any designated monitoring. This may lead to poorer adherence compared to warfarin. Previous studies have yielded conflicting results. Importantly, no study has adequately adjusted for the fact that warfarin dosing is continuously modified according to INR values, while DOACs are prescribed at fixed doses.
Aims: To compare adherence rates between different oral anticoagulants (OACs) in a nationwide cohort.
Methods: Data on all OAC naïve patients who received OAC prescription from 2014-2019 were collected from the Icelandic Medicine Registry and Landspitali University Hospital. We calculated the mean daily dose of warfarin for each patient using data from Landspitali Anticoagulation Management Center, which had information on dose adjustments for 72% of patients receiving warfarin in Iceland during the study period. Patients receiving warfarin with missing data on dose adjustments were excluded. Adherence was estimated by mean daily doses using proportion of days covered (PDC). Patients with PDC below 80% were considered nonadherent. Patients receiving warfarin, rivaroxaban, apixaban, and dabigatran were matched for age, gender, comorbidities, and area of residency using inverse-probability weighing.
Results: Our cohort included 1,002 patients receiving warfarin, 2,909 receiving rivaroxaban, 1,999 apixaban, and 425 dabigatran. Warfarin had the highest adherence rate (91.8%, 95%CI 90.6-92.9%), followed by rivaroxaban (89.2%, 88.6-89.9%), apixaban (87.5%, 86.7-88.4%), and dabigatran (81.2%, 79.1-83.4%) (Figure 1). Similarly, rates of nonadherence were lowest for warfarin (12.0%, 95%CI 10.0-14.0%), followed by rivaroxaban (22.1%, 20.6-23.6%), apixaban (24.4%, 22.5-26.3%), and dabigatran (43.3%, 38.6-48.0%) (Figure 2). Using logistic regression, the odds of nonadherence compared to warfarin was 2.1 (95%CI 1.7-2.6), 2.4 (1.9-3.0), and 5.6 (4.2-7.4) for rivaroxaban, apixaban, and dabigatran, respectively.
Conclusions: Warfarin was associated with higher adherence rates compared to DOACs. The highest non-adherence rates were observed with dabigatran, followed by apixaban and rivaroxaban.
[Figure 1: Comparison of adherence between different oral anticoagulants using proportion of days covered.]
[Figure 2: Comparison of nonadherence rates between different oral anticoagulants. Nonadherence was defined as proportion of days covered below 80%.]
To cite this abstract in AMA style:
Ingason AB, Hreinsson JP, Agustsson AS, Lund SH, Reynisson IE, Gudmundsdottir BR, Onundarson PT, Bjornsson ES. Comparison of Medication Adherence Between Different Oral Anticoagulants: A Propensity Weighted Nationwide Cohort Study [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/comparison-of-medication-adherence-between-different-oral-anticoagulants-a-propensity-weighted-nationwide-cohort-study/. Accessed March 21, 2024.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/comparison-of-medication-adherence-between-different-oral-anticoagulants-a-propensity-weighted-nationwide-cohort-study/