Adherence to anticoagulants in people with stroke and atrial fibrillation: Implementation of standardized analytic...

Post-stroke medication adherence can be assessed using dispensing data; however, variations in methods hinder reliable comparisons across regions.

To develop and implement standardized methods to compare medication adherence to direct oral anticoagulant post-stroke between countries.

An observational study was conducted across two countries participating in the International Network for Standardised Population Insights and Real-world Evidence for STROKE. Australia and Canada, with population-based linked administrative data, provided the case example. Metadata structures were shared to harmonize variables and response options in linked administrative data. Patients admitted with incident ischemic stroke and atrial fibrillation (Victoria, Australia (July 2014-June 2017); Ontario, Canada (July 2014-March 2022)), aged ⩾65 years, who survived ⩾90 days post-discharge were included. The proportion of days covered of direct oral anticoagulants was measured from initiation to 1-year post-discharge. Adherence was measured using a standardized code from the TEN-SPIDERS pharmacoepidemiology framework. Seven simulations were undertaken adjusting for different proportion of days covered measurement parameters (e.g. in-hospital stays, pre-supply, survival, and early refills and switching). Aggregated outputs were compared between countries.

Among 2471 Australians (50% female; 36% aged 85+ years) and 16,622 Canadians (51% female; 34% aged 85+ years), 50% and 65% were dispensed a direct oral anticoagulant within 90 days post-stroke, respectively. Among initiators, median 1-year direct oral anticoagulant proportion of days covered was 86.8% (interquartile range: 75.9-92.6%) in Australia versus 96.2% (interquartile range: 89.6-98.6%) in Canada. Simulations adjusting for pre-supply, early refills, and switching increased median proportion of days covered by +10.3% in Australia and +3.5% in Canada. Further adjustment for in-hospital stays had negligible impacts on proportion of days covered.

Implementation of standardized methods across two countries revealed high levels of adherence to direct oral anticoagulants in patients with ischemic stroke and atrial fibrillation. Scale-up of these methods to other countries and medications is warranted to reliably measure and compare trends in post-stroke medication adherence.