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Apixaban for Stroke Prevention in Atrial Fibrillation: Why are Event Rates Higher in Clinical Practice than in
Tim A C de Vries1,2,3, Jack Hirsh4,5, Ke Xu1,6
1Population Health Research Institute, Hamilton, Ontario, Canada.
Thrombosis and Haemostasis
|July 16, 2020
Summary
Off-label use of apixaban 2.5 mg twice daily is common in real-world practice. Higher risk patient profiles in observational studies, not just dosing, contribute to increased thromboembolic events and mortality.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Research
Background:
- Frequent off-label use of apixaban 2.5 mg twice daily is suspected to increase thromboembolic events in observational studies (OSs) compared to randomized controlled trials (RCTs).
- This has led to recommendations against its use in all patients.
Purpose of the Study:
- To investigate factors contributing to higher thromboembolic event rates.
- To estimate the prevalence of off-label apixaban use in current practice.
- To compare patient characteristics and outcomes (stroke, bleeding, mortality) based on apixaban dose and study design.
Main Methods:
- A systematic review and meta-analysis of 18 OSs and 2 RCTs.
- Inclusion of 155,228 patients from OSs and 11,928 patients from RCTs.
- Comparison of apixaban 2.5 mg twice daily versus 5 mg twice daily use and outcomes across study designs.
Main Results:
- Patients in OSs were more likely to receive apixaban 2.5 mg twice daily (31.3% vs. 5.1%), were older, and had higher CHA2DS2-VASc scores than those in RCTs.
- Higher rates of thromboembolic events, bleeding, and mortality were observed with apixaban 2.5 mg twice daily compared to 5 mg twice daily in both OSs and RCTs.
Conclusions:
- Differences in patient risk profiles between OSs and RCTs are significant contributors to observed thromboembolic event rates.
- Higher rates of bleeding and mortality with apixaban 2.5 mg twice daily, beyond thromboembolism, suggest patient characteristics are key factors in clinical practice outcomes.
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