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Specimen Collection Manual and Test Catalog

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VON WILLEBRAND (VWF:AG) FACTOR ANTIGEN

Geisinger Epic Procedure Code:  LAB3266    Geisinger Epic ID:  21475

SPECIMEN COLLECTION
Specimen type: 

Platelet-poor plasma


Preferred collection container: 
Alternate collection container: 
Other size blue-top (3.2% sodium citrate) tubes (e.g., 1.8 mL, 4.5 mL)
Specimen required: 

1 mL


Special notes: 
  • If the patient’s hematocrit (HCT) is >55%, the volume of anticoagulant in the tube must be adjusted. Contact a performing location for sodium citrate adjusted tubes or instruction for how to adjust the sodium citrate.
  • When possible, use fresh venipuncture.
  • Avoid prolong tourniquet time (< 1 minute) and hemolysis during collection as this will alter results.
  • If indwelling catheter or butterfly collection device must be used, draw sample from a non-heparinized lumen or flush the line with 5 mL of saline and discard first 10 mL of blood.
  • Tubes should be >90% filled.
  • Immediately mix gently after collection by inverting the tube end over end 5 to 6 times. Avoid vigorous mixing or additional inversion. Observe for the presence of clots or hemolysis and recollect if observed.


SPECIMEN PROCESSING
Processing instructions: 

Centrifuge specimen immediately at designated time and speed to obtain platelet-poor plasma (<10,000/µL). Using a plastic pipette, carefully remove plasma from cells, avoiding platelet/buffy layer by leaving a thin layer of plasma on top the cells. The centrifuged plasma should be aliquoted (1 mL per aliquot) into clearly labeled polypropylene tubes. The number of tests ordered will determine the aliquots needed. Check the residual specimen for clot and if present discard sample and redraw specimen. If plasma is icteric, lipemic or hemolyzed a lab comment should be generated to notify staff. Freeze upright in non-thaw freezer.


Transport temperature: 

Frozen on dry ice


Specimen stability: 

Room temperature (whole blood): 4 hours 
Room temperature (plasma off cells): 8 hours 
Frozen (plasma) -20°C: 30 days
Frozen (plasma) -70°C: 6 months


Rejection criteria: 

Clotted, hemolyzed, grossly icteric, grossly lipemic, improperly filled tubes, improper anticoagulant ratio (HCT >55% and citrate not adjusted), refrigerated specimens, or stability exceeded

Note: Specimen suspected of thawing in transport, indicated by slant in aliquot or specimen in lid of tube, will have testing performed, and the comment “interpret results with caution as thawing suspected” added to results.



TEST DETAILS
Reference interval: 

50-160%


Additional information: 

Anticoagulation Impact on Coagulation Tests


CPT code(s):  85246
Note: The billing party has sole responsibility for CPT coding.  Any questions regarding coding should be directed to the payer being billed.
The CPT codes provided by GML are based on AMA guidelines and are for informational purposes only.

Test includes: 

Factor VIII related Antigen Level


Methodology: 
Immunoturbidometric
Synonyms: 

VIII Ag, FA8AG, VWF


Clinical significance: 

Von Willebrand factor (VWF) is a glycoprotein synthesized in megakaryocytes and endothelial cells that is utilized in primary hemostasis (platelet aggregation) and as a carrier site for the clotting factor VIII. Decreased quantity and/or functionality of VWF leds to mucocutaneous bleeding and menorrhagia. Low VWF levels can be observed in acquired or congenital von Willebrand disease (VWD)

Von Willebrand factor antigen (VWF:Ag) assay is one type of test used to assess for VWD. It is a quantitative assessment of the patients VWF antigen. It is typically part of a panel of tests (including factor VIII activity and VWF antigen). Abnormalities could be suggestive of a VWD.


Doctoral Director(s): 
Michelle Grant DO
Review Date:  03/04/2025

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