abnormal circulating protein level abnormal circulating von Willebrand factor level 2020-09-21T10:08:42Z abnormal plasma von Willebrand factor level abnormal circulating vWF level any anomaly in the blood level of the large multimeric glycoprotein produced by vascular endothelial cells and megakaryocytes that chaperones blood coagulation cofactor factor VIII and tethers platelets to the injured blood vessel wall MPheno.ontology abnormal plasma vWF level abnormal plasma VWF level MP:0031163 abnormal circulating VWF level