Excerpt
Beside their presence on red blood cells (RBCs), ABO blood group antigens are expressed on the surface of a variety of human cells and tissues, including the epithelial cells, sensory neurons, platelets, and the vascular endothelium [
1]. It is therefore plausible from a biological point of view that ABO antigens could be involved in the development of a wide array of human diseases, such as infectious disorders, cancers, and cardiovascular diseases [
2‐
6]. Robust evidence exists also on the close link between ABO antigens and hemostasis: it is well known, indeed, that in individuals with non-O blood type von Willebrand factor (VWF) levels are approximately 25% higher than individuals with O blood group. The underlying molecular mechanism resides in the ABO-related different glycosylation pattern of VWF, which strongly influences its clearance and, consequently, its functional levels [
7]. A number of clinical studies have consistently documented the relationship between the ABO blood group system and the risk of developing thrombotic disorders [
2]; in particular, individuals belonging to non-O blood type carry an approximately double increased risk of venous thromboembolism compared with O blood type subjects [
8]. By contrast, it is still debated if the latter are predisposed to an increased hemorrhagic risk [
9]. For instance, Leonard and colleagues [
10] observed a disproportionately high prevalence of blood group O compared with the general population (68 vs. 55%,
P = 0.01) in a retrospective study on 303 patients suffering from post-tonsillectomy hemorrhages. In a case-control study on 549 patients under vitamin K antagonist (VKA) therapy, we showed that O blood group was associated with an increased risk of developing more severe bleeding [
11]. In a subsequent retrospective study on 676 patients with major hemorrhagic events, we found that O blood type predisposed to severe gastrointestinal bleeding in the cohort of patients under VKA therapy [
12]. Interestingly, a recent study by Hazendonk and colleagues has documented that blood group O is associated with an increased perioperative bleeding in naturally anticoagulated hemophilia A patients [
13]. Conversely, other studies did not confirm the higher bleeding tendency associated with blood group O [
14,
15]. Thus, in order to further clarify this controversial issue, we conducted a retrospective study to assess whether there was a correlation between O blood group and the risk of developing bleeding from the upper gastrointestinal tract. …
