The vWF:Ac assay seems to be less affected by high bilirubin, free hemoglobin, lipidemia or genetic polymorphism than vWF:RCo and, therefore, allows for more reliable screening of avWS with loss of HMW multimers—especially in the setting of heart valve disease and mechanical circulatory support [18, 19]. Here, VWF is linked to hyperlipidemia.