Patients suffering from innate or acquired platelet disorder (i.e. HIT, TTP, HUS, ITP, sepsis, haemato-oncological disease, other hereditary thrombocytopathies)—with the exception of prior treatment with single or dual antiplatelet agents—or disease affecting vWF (i.e. von Willebrand disease, haemophilia A) will be excluded from the study in order to be able to reliably assess the effect of vWF when added to platelets. The gene discussed is VWF; the disease is autoimmune thrombocytopenic purpura.