{"id":"vwf-activity","name":"von Willebrand Factor Activity (Ristocetin Cofactor / GPIb Binding)","shortName":"VWF Activity","aliases":["von Willebrand Factor Activity","vWF Activity","vWF Ristocetin Cofactor","VWF:RCo","Ristocetin Cofactor","vWF:GPIbM","vWF Activity (GPIb Binding)","VWF:GPIbR","von Willebrand Factor Activity, Plasma","von Willebrand Factor Activity, P","von Willebrand Factor Activity (Ristocetin Cofactor)","von Willebrand Factor (VWF) GPIbM Activity","von Willebrand Factor, Activity (RCF)","Ristocetin Cofactor, Plasma","VWF Ristocetin Cofactor Activity"],"abbreviations":["VWF:RCo","VWF:GPIbM","VWF:GPIbR","VWF:Act","VWF:A"],"loinc":[{"code":"68324-3","primary":true},{"code":"6014-5","primary":false},{"code":"107372-5","primary":false},{"code":"107378-2","primary":false},{"code":"4680-5","primary":false}],"specimen":"plasma","units":[{"ucum":"%","display":"%"},{"ucum":"[IU]/dL","display":"IU/dL"},{"ucum":"[IU]/mL","display":"IU/mL"}],"referenceRanges":[{"population":"18+","low":51,"high":215,"unit":"%","unitDisplay":"%","note":"ARUP Laboratories interval for ages 18 and over, both sexes. ARUP lists the same interval for its ristocetin cofactor (RCo) test and its GPIbM test. Other labs differ: Mayo Clinic Laboratories (latex immunoassay) lists 55–200%, UW Medicine (GPIb-binding latex immunoassay) lists 50–200%, and Indiana University Health lists 43–195% for its VWF activity screen. People with blood group O often have lower VWF. Mayo notes that apparently healthy people in group O can have activity as low as 40% to 50%, while the lower limit for other blood groups may be 60% to 70%. The 2021 ASH/ISTH/NHF/WFH guideline says ABO-specific ranges are not required and that the lab's own lower limit should be used if it is below 50%. Use the range printed on your own report.","sources":[{"title":"von Willebrand Factor Activity (Ristocetin Cofactor) (test 0030250)","url":"https://ltd.aruplab.com/Tests/Pub/0030250","publisher":"ARUP Laboratories"},{"title":"von Willebrand Factor (VWF) GPIbM Activity (test 3019671)","url":"https://ltd.aruplab.com/Tests/Pub/3019671","publisher":"ARUP Laboratories"},{"title":"von Willebrand Factor Activity, Plasma (test ID VWACT)","url":"https://www.testcatalog.org/show/VWACT","publisher":"Mayo Clinic Laboratories (Extended Catalog, via testcatalog.org)"},{"title":"Thrombosis & Hemostasis Reference Ranges (updated 1/11/2021)","url":"https://cdn.iuhealth.org/resources/Thrombosis-Hemostasis-Ref-Ranges-No-StarMax.pdf","publisher":"Indiana University Health Pathology Laboratory","year":2021},{"title":"von Willebrand Disease Profile, Plasma (test ID AVWPR)","url":"https://www.testcatalog.org/show/AVWPR","publisher":"Mayo Clinic Laboratories (Extended Catalog, via testcatalog.org)"},{"title":"ASH ISTH NHF WFH 2021 guidelines on the diagnosis of von Willebrand disease","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7805340/","publisher":"Blood Advances","year":2021},{"title":"Von Willebrand Factor Activity (test code VWFACT)","url":"https://dlmp.uw.edu/test-guide/view/VWFACT","publisher":"UW Medicine, Department of Laboratory Medicine and Pathology"}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"Measures how well von Willebrand factor helps platelets stick to a wound. It is one of the main tests used to look into von Willebrand disease.","url":"https://bloodtesttracker.com/markers/vwf-activity","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}