von Willebrand Factor Activity with Reflex to Ristocetin Cofactor Activity


Abbrev Code:VWACTR   
Order Code:LAB6598Order Name:VWF Activity Reflex to Ristocetin Cofactor
Synonyms:VWF Activity to Ristocetin Cofactor Activity
Methodology:Immunoassay; platelet agglutination (if reflexed)
CPT Codes: 85245 x1, 85245 x1, 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. If testing reflexes to ristocetin cofactor activity, specimens are sent to reference lab Mon-Sat and resulted within 1-3 days.
Special Instructions: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, von Willebrand Factor (VWF) Screen Algorithm, Specimen Collection and Processing for Coagulation Specimens


Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on tube.
Minimum\Peds Volume:2.7 mL (in 3 mL tube) - filled to fill line on tube.
Container:
Alternate Containers: 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:This testing is used in the diagnosis of von Willebrand disease. Von Willebrand Factor Antigen will be performed on all samples. Ristocetin Cofactor Activity will be performed if von Willebrand Factor Activity is less than or equal to 50%, von Willebrand Factor Antigen is less than or equal to 50%, or von Willebrand Factor Activity to von Willebrand Factor Antigen ratio is less than or equal to 0.70. Reflex testing may also be sent following communication between pathologist and provider. See Associated Links to algorithms.


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