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Von Willebrand Factor Activity

Important Note

For evaluation of von Willebrand's Disease order: von Willebrand factor activity, von Willebrand factor antigen and Factor 8 assay.

eD-H Order Code

LAB335

Specimen Collection Information

Specimen Minimum Test Volume Container Special Handling
Blood

PEDI, PICU, or ICN draws refer to specimen collection job aid.

All other Coag tubes must be filled to the line on tube.

 Fill tube completely

Specimen Transport Temperature

Double spin and freeze

Reference Ranges/Critical Values

Assay Gender Age Range Normal Range Critical Values Units
von Willebrand Factor Activity All All >50    

Specimen Stability

4 hours

Additional Specimen Instructions

1.8 mL Sodium Citrate tube filled to the line

OR

2.7 mL Sodium Citrate tube filled to the line

 

 

Blue top tubes must be filled within 10% of stated volume. A discard tube must be used if a citrate tube is to be drawn using a winged blood collection set. It is important to remove air from the blood collection set to ensure the proper blood volume is obtained in the coag tube.

 

If the patient has a known hematocrit >55%, please contact the coagulation lab for an adjusted collection tube before drawing the blood.

 

 

Interpretive Data

Assay Interpretive Data
von Willebrand Factor Activity Current guidelines recommend a diagnosis of von Willebrand disease in patients with von Willebrand factor antigen and/or activity levels <30%  regardless of bleeding history.   In patients with a clinical history of abnormal bleeding  von Willebrand factor antigen and/or activity levels of 30-50% are sufficient for the diagnosis of type 1 von Willebrand disease as individuals with these levels may demonstrate a mild bleeding diathesis.   Emotional or physiologic stress may elevate VWF levels into the normal range. If von Willebrand factor antigen and/or activity levels are </=55% and von Willebrand disease is strongly suspected clinically  repeat testing may be appropriate.   Reference: James PD  et al. ASH ISTH NHF WFH 2021 guidelines on the diagnosis of von Willebrand disease. Blood Adv. 2021 Jan 12;5(1):280-300. PMID:33570651

 

CPT(s)

85245

Performing Lab Section

Hematology

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