College of American Pathologists
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Blood group and thrombosis

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November 2000

The association between high levels of factor VIII and risk of venous thrombosis, which the Leiden group first described in 1995, explains observations from the 1960s of a relationship between certain blood groups (A, B, or AB) and a higher risk of thrombosis, says LETS study investigator and clinical epidemiology professor F.R. Rosendaal, MD, PhD, of the Hemostasis and Thrombosis Research Center, Leiden University Medical Center.

"The explanation," he told CAP TODAY, "is that blood group O is associated with lower levels of von Willebrand factor and therefore with lower levels of factor VIII-since von Willebrand factor is the carrier protein of factor VIII, which is much more readily degraded when not bound to vWF."

These two relations-blood group with vWF and vWF with factor VIII-were known for many years prior to their study, he says. "In the 1995 paper, we showed that factor VIII really is the final effector of the risk. Since blood group is genetic, the issue of adjustment for other factors becomes less relevant-other factors cannot affect blood group."