High Von Willebrand Factor Activity: Clinical Significance
You are correct—high Von Willebrand factor (VWF) activity is generally not clinically concerning for bleeding disorders, as it is the deficiency or dysfunction of VWF that causes bleeding problems. 1
Why High VWF Activity Typically Doesn't Indicate a Bleeding Problem
- VWF is an acute phase reactant, meaning its levels naturally increase in response to stress, inflammation, recent exercise, pregnancy, and oral contraceptive use 1, 2
- Elevated VWF levels do not impair hemostasis—the protein functions to promote platelet adhesion and clotting, so having more of it does not cause bleeding 3, 4
- Von Willebrand disease (VWD) results from low or dysfunctional VWF, not elevated levels 1, 5
When Low VWF Activity Matters
- Definitive VWD diagnosis typically requires VWF activity (VWF:RCo) <30 IU/dL 2
- Normal VWF activity ranges from 50-200 IU/dL 2
- VWF activity between 30-50 IU/dL may still represent VWD if there is supporting clinical or family history of bleeding 2
Important Clinical Context
Testing Considerations
- VWF testing must often be repeated up to 3 times to ensure reliable results due to the variability of VWF as an acute phase reactant 1
- The VWF:RCo assay has high coefficient of variation (10-30%), which can affect interpretation 2
- Blood type O individuals naturally have lower VWF levels (approximately 25% lower than non-O blood types), which must be considered when interpreting results 2
When to Test for VWF Activity
- Testing is indicated when evaluating bleeding symptoms such as mucocutaneous bleeding, easy bruising, epistaxis, menorrhagia, or bleeding with surgery 1, 6
- In patients starting ibrutinib therapy with a history of bleeding, testing for VWF activity is reasonable, as acquired von Willebrand syndrome can occur with high IgM levels 1
The Bottom Line
High VWF activity does not suggest a bleeding disorder and requires no intervention. 1 The clinical concern is exclusively with low or dysfunctional VWF, which impairs platelet adhesion and causes bleeding manifestations. 5, 3 If VWF activity is elevated, this likely reflects physiologic stress response or inflammation rather than any pathologic process affecting hemostasis. 1, 2