title: Relationship between ABO blood group and hemorrhage: a systematic literature review and meta-analysis.
abstract: Several studies have suggested that patients with non-O blood group have an increased risk of both venous and arterial thromboembolic events. On the contrary, the role of ABO blood group on the risk of bleeding complications remains unclear. Thus, we performed a meta-analysis of the literature with the aim of assessing this potential association. MEDLINE and Embase databases were searched from 1946 to March 2012. Studies comparing the prevalence of different ABO blood groups in bleeding patients as well as in controls without bleeding complications were potentially includible. Two reviewers independently selected studies and extracted study characteristics, quality, and outcomes. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each trial and pooled using a random-effects model. Twenty-two studies totalling 9,468 bleeding patients and more than 450,000 controls were included. The prevalence of O blood group was significantly higher in bleeding patients than in controls, with a resulting pooled OR of 1.33 (95% CI = 1.25 to 1.42; p < 0.001). The result of this meta-analysis of a very large sample of bleeding patients and controls suggests that O blood group is a potentially important genetic risk factor for bleeding. High-quality prospective studies are warranted to confirm these preliminary findings.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Insubria, Varese, Italy. fdentali@libero.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Dentali
authors.forename: Anna Paola
authors.initials: AP
authors.lastname: Sironi
authors.forename: Walter
authors.initials: W
authors.lastname: Ageno
authors.forename: Carlo
authors.initials: C
authors.lastname: Bonfanti
authors.forename: Silvia
authors.initials: S
authors.lastname: Crestani
authors.forename: Francesco
authors.initials: F
authors.lastname: Frattini
authors.forename: Luigi
authors.initials: L
authors.lastname: Steidl
authors.forename: Massimo
authors.initials: M
authors.lastname: Franchini
mesh_terms: D000017:ABO Blood-Group System; D006470:Hemorrhage / Q000097:blood*; D006801:Humans; D016017:Odds Ratio; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D000017:ABO Blood-Group System