Don’t order isolated von Willebrand factor antigen (VWF:Ag) or von Willebrand factor activity (VWF:Act) assays alone. When von Willebrand disease is indicated, order a von Willebrand disease profile consisting of VWF:Ag, VWF:Act, and FVIII coagulant activity.
VWD is the name for a family of disorders characterized by VWF deficiency or dysfunction and is the most prevalent congenital systemic bleeding disorder. VWD test results indicate potential VWD in ~1% of the global population, and VWD accounts for 1 in 20,000 urgent care and emergency department visits for major bleeding. Symptom severity varies among kindreds and in individuals over time. Laboratory detection requires a FVIII activity assay, a quantitative VWF:Ag assay, and a functional VWF:Act assay. Several VWF:Act assays are available, both clot-based and immunoassays, offering varying specificity and sensitivity. The combination of three initial assays’ results enables the provider to make a preliminary diagnosis of VWD type 1, 2, or 3, and triggers an algorithm-based follow-up protocol to confirm the diagnosis.
George recently shared this recommendation with Prof. Malissa Norfolk who commented, “I’ve seen VWF:Act or VWF:Ag used alone in rheumatology patients. I don’t know why they use it except perhaps to monitor inflammation, but I’ve seen it consistently from the rheumatology department.”
Inflammatory Processes: VWF:Ag is an acute-phase reactant that is a hallmark of many rheumatic diseases. Raised VWF:Ag levels have been observed in patients with vasculitis, often without elevation of the ESR. Elevated VWF:Ag levels have also been reported in patients with SLE and RA.
Potential Biomarker: Some studies suggest that VWF:Ag levels may identify changes in disease activity during follow-up and help to predict treatment response.
Limitations: VWF:Ag levels are influenced by blood group, pregnancy, and exercise.
From Bob Gosselin: I don’t recollect seeing this used at my old haunts for this indication. This seems like a coagulation test that outsiders use thinking it will have high specificity for their indication. I’m not sure how a person with a VWF:Act/Ag ratio of 1, but values in the low 40s (such as in blood group O), can profit from this test as a marker of vascular inflammation since doubling/tripling would still be within normal limits. Perhaps it is of limited value to monitor efficacy if there is a reduction of VWF after therapy. This could work so long as the blood collection is obtained with good clinical practice that avoids prolonged tourniquet time and timing like not after running up a flight of stairs.
I am very acquainted with rheumatology disorders since I have rheumatoid arthritis. My rheumatologist has never ordered any coagulation tests for any indication of VWF disorder testing. I will take this up with her in about two weeks.