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Bleeding risk in randomized controlled trials comparing warfarin and aspirin: a systematic review and meta-analysis
A E Warkentin1, M P Donadini, F A Spencer
1Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
Insights
Warfarin and aspirin (ASA) are common cardiovascular drugs. This meta-analysis found no significant difference in major bleeding risk between them, though warfarin showed a trend towards increased intracranial bleeding.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Trials
Background:
- Warfarin and aspirin (acetylsalicylic acid [ASA]) are widely prescribed for cardiovascular disease.
- Understanding their comparative bleeding risks is crucial for patient management.
Purpose of the Study:
- To pool data from randomized controlled trials (RCTs).
- To estimate the bleeding risk associated with warfarin versus ASA at guideline-recommended doses.
Main Methods:
- Systematic literature search of Ovid MEDLINE, Embase, and Cochrane Library up to September 2011.
- Inclusion of RCTs comparing warfarin (target INR 2.0-3.5) with ASA (50-650 mg daily) in adult patients with at least 3 months follow-up.
- Meta-analysis using inverse variance and random effects models to calculate pooled odds ratios (ORs) and 95% confidence intervals (CIs).
Main Results:
- Eight RCTs involving 2904 patients were analyzed.
- A trend towards increased major bleeding risk with warfarin was observed (OR 1.27; 95% CI 0.83-1.94).
- Minor bleeding was significantly more common with warfarin (OR 1.50; 95% CI 1.13-2.00), with a trend for increased intracranial hemorrhage (OR 1.64; 95% CI 0.71-3.78).
Conclusions:
- No statistically significant difference in major bleeding was found between warfarin and ASA at recommended doses.
- The observed trend for increased bleeding with warfarin may be attributed to a higher incidence of intracranial bleeding.
Background:
Warfarin and aspirin (acetylsalicylic acid [ASA]) are the most commonly used anticoagulant and antiplatelet drugs in the treatment of cardiovascular disease.
Objectives:
To provide a pooled estimate of the bleeding risk from randomized controlled trials (RCTs) comparing warfarin and ASA at the dose ranges recommended in evidence-based guidelines.
Patients/Methods:
Ovid MEDLINE, Embase and the Cochrane Library, up to September 2011, were searched for RCTs comparing bleeding rates in adult patients randomized to warfarin, target International Normalized Ratio (INR) 2.0-3.5, and ASA, 50-650 mg daily, with at least 3 months of follow-up. Pooled odds ratios (ORs) and associated 95% confidence intervals (CIs) were calculated with the inverse variance method and the random effects model.
Results:
Four thousand four hundred and forty-two abstracts were screened, resulting in eight included studies for final analysis. A pooled estimate derived from the 2904 patients enrolled indicated a trend towards an increase in major bleeding risk in those randomized to warfarin (OR 1.27; 95% CI 0.83-1.94). The pooled OR for intracranial hemorrhage in patients treated with warfarin vs. ASA was 1.64 (95% CI 0.71-3.78), and that for extracranial major bleeding was 1.03 (95% CI 0.61-1.75). Minor bleeding, from a 1748-patient sample, was more common in warfarin patients (OR 1.50; 95% CI 1.13-2.00).
Conclusions:
This meta-analysis failed to find a statistically significant difference in major bleeding between warfarin, target INR 2.0-3.5, and ASA, 50-650 mg daily. The trend towards increased bleeding with warfarin appears to be explained by an excess of intracranial bleeding in warfarin patients.
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