Warfarin-Associated Bleeding and Thromboembolic Events in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

Abstract

Background: Warfarin use in Sub-Saharan Africa is associated with elevated risks of thromboembolic events and bleeding, but precise prevalence estimates are lacking. This systematic review and meta-analysis aimed to quantify the prevalence of bleeding and thromboembolic events among patients on warfarin in Sub-Saharan Africa. Methods: Comprehensive searches were conducted in MEDLINE via Ovid, PubMed, Embase via Ovid, Scopus, and Google Scholar to identify relevant studies. Primary outcomes included major and minor bleeding events, while thromboembolic events were secondary outcomes. Meta-analysis was conducted using RStudio version 4.3.3 with the meta and metaprop packages. Proportions were transformed using the Freeman–Tukey double arcsine method, and meta-regression was performed with the metafor package's escal, rma, and res functions. Publication bias was assessed via funnel plots and Egger's test, with a p value < 0.05 indicating potential bias. Sensitivity analysis was conducted through leave-one-out analysis. The review was performed in adherence to PRISMA guidelines. Results: We identified 10 observational studies for inclusion in this systematic review and meta-analysis. Egger's test indicated no publication bias. Meta-regression analysis showed that moderators (publication year, sample size, setting, and follow-up duration) did not significantly impact bleeding risk. The pooled prevalence of major and minor bleeding was 18% (95% CI: 0.10–0.27; I2: 96%, prediction interval: 0.00–0.53), with rates ranging from 4% to 46%. Thromboembolic events occurred in 7% of warfarin users (95% CI: 0.01–0.07). Conclusion: Warfarin therapy in Sub-Saharan Africa is associated with considerable bleeding and thromboembolic risks. The robustness of these findings was confirmed through meta-regression and sensitivity analyses, underscoring the need for improved therapeutic monitoring and safety strategies in this population.