Adherence to anticoagulants in people with stroke and atrial fibrillation: Implementation of standardised analytic methods in Australia and Canada

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

Aim — To develop and implement standardised methods to compare medication adherence to direct oral anticoagulants (DOACs) post-stroke between countries.

Methods — An observational study was conducted across two countries participating in the International Network for Standardised Population Insights and Real-world Evidence for STROKE (INSPIRE-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 ischaemic 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 (PDC) of DOACs was measured from initiation to 1-year post-discharge. Adherence was measured using standardised code from the TEN-SPIDERS pharmacoepidemiology framework. Seven simulations were undertaken adjusting for different PDC measurement parameters (e.g., in-hospital stays, pre-supply, survival, early refills and switching). Aggregated outputs were compared between countries.

Results — Among 2471 Australians (50% female; 36% aged 85+ years) and 16622 Canadians (51% female; 34% aged 85+ years), 50% and 65% were dispensed a DOAC within 90 days post-stroke, respectively. Among initiators, median 1-year DOAC PDC was 86.8% (interquartile range [IQR]: 75.9%–92.6%) in Australia vs 96.2% (IQR: 89.6%–98.6%) in Canada. Simulations adjusting for pre-supply, early refills, and switching increased median PDC by +10.3% in Australia and +3.5% in Canada. Further adjustment for in-hospital stays had negligible impacts on PDC.

Conclusions — Implementation of standardised methods across two countries revealed high levels of adherence to DOACs in patients with ischaemic 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.