It has been well known for many years that the ABO blood group has a major influence on hemostasis, through its influence on von Willebrand factor and, consequently, factor VIII plasma levels. Although the relationship between non-O blood type and the risk of venous thromboembolism is nowadays also well established, the association with arterial thrombotic events (i.e., myocardial infarction [MI] and ischemic stroke) is less well characterized. To elucidate the latter issue, we have conducted a systematic review and meta-analysis of the existing literature. After an electronic search strategy using MEDLINE and EMBASE and a manual review of abstract books of the International Society on Thrombosis and Haemostasis and of reference lists of all retrieved articles, 28 studies were finally included in our systematic review. The prevalence of non-O blood group was significantly higher in patients with MI (pooled odds ratio [OR]: 1.28, 95% confidence interval [CI]: 1.17-1.40; p < 0.001) and ischemic stroke (pooled OR: 1.17, 95% CI: 1.01-1.35; p = 0.03) than in controls. The restriction of the analysis to high quality studies only confirmed the association with MI (pooled OR: 1.17, 95% CI: 1.03-1.32) but not with ischemic stroke (pooled OR: 1.28, 95% CI: 0.94-1.74). In conclusion, the results of our meta-analysis confirm the existing literature evidence of a weak association between non-O blood group and vascular arterial thrombosis, in particular myocardial ischemia.
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