von Willebrand Factor Activity


Sunquest Code:VWACT  
Epic Code:LAB6597  
Order Instructions:Outreach clients order: NCBAT
Synonyms:VWF activity
Methodology:Immunoassay
CPT Code:85245
Turnaround Time:Specimen is accepted/processed 24 hours/day. Test is performed 2-3 times/week; results are reported within 2-7 days. Available stat if urgent.
Special Instructions:This assay is not the Ristocetin Cofactor Activity assay.
Associated Links:

von Willebrand Factor (VWF) Panel Algorithm, Specimen Collection and Processing for Coagulation Specimens, von Willebrand Factor (VWF) Screen Algorithm



Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tube or clotted specimens. Hemolyzed, icteric or lipemic specimens.


Processing and Shipping

Specimen Processing:See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab Special Coagulation  (UMMC-East Bank)


Interpretive

Critical Range:Less than 19%
Reference Range:

1-4 d

50-287%

5-29 d

50-254%

30-89 d

50-246%

90-179 d

50-206%

180-364 d

50-197%

1 y and older

50-180%

Age specific reference ranges have not been established for the von Willebrand Activity in newborns (0 day).

 

Use:The diagnosis of von Willebrand's Disease (VWD) probably the most common congenital bleeding disorder, requires a number of special tests at the laboratory level. The measurement and comparison of von Willebrand Factor Antigen (VWF:Ag), VWF Activity and Factor VIII (FVIII) levels in plasma aid in the differentiation of quantitative defects (type 1 or type 3) or qualitative defect (type 2) of VWF and therefore to diagnose the different types of VWD. The activity of VWF is determined by measuring the increase of turbidity induced by the agglutination of a latex particle reagent. A specific anti-VWF monoclonal antibody adsorbed onto the latex reagent, directed against the platelet binding site at VWF (Glycoprotein 1b receptor) reacts with the VWF of patient plasma. The degree of agglutination is directly proportional to the activity of VWF in the patient plasma. THIS ASSAY IS NOT A RISTOCTIN COFACTOR ACTIVITY ASSAY. The presence of rheumatoid factor may produce an overestimation of the von Willebrand factor activity test result.


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