von Willebrand Factor Activity


Abbrev Code:VWACT   
Order Code:LAB6597  
Synonyms:VWF activity
Methodology:Immunoassay
CPT Codes: 85245 x1, 85245 x1
Turnaround Time:Turnaround time is 5 days, testing performed 2-3 day per week. With pre-notification, STATs are done within 1 hour after receipt in the testing laboratory.
Special Instructions:This assay is not the Ristocetin Cofactor Activity assay. Usually performed as part of a von Willebrand screen or panel with Factor 8 activity and von Willebrand Antigen.
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.
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit.


Processing and Shipping

Specimen Processing:
  • Process for Platelet Poor Plasma within 4 hours of collection.
  • Aliquot plasma, place clear tape around label, and freeze at -20C or on dry ice within 4 hours of collection.
  • If multiple tests are collected on 1 blue top, split each blue top into 2 aliquots. Minimum 0.5 mL per tube.
  • A maximum of 6 aliquots are needed per collection.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:
  • Ensure specimen is frozen before shipping.
  • Ship on dry ice, sample must remain frozen during shipping.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab UM Special Coag (K)  (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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