von Willebrand Factor Activity with Reflex to Ristocetin Cofactor Activity


Sunquest Code:VWACTR  
Epic Code:LAB6598Epic Name:VWF Activity Reflex to Ristocetin Cofactor
Synonyms:VWF Activity to Ristocetin Cofactor Activity
Methodology:Immunoassay; platelet agglutination (if reflexed)
CPT Code:85245, 85245
Turnaround Time:Specimen is accepted/ processed 24 hrs/day, and is performed 1-3 times/week; results are reported within 2-7 days. If testing reflexes to ristocetin cofactor activity, specimens are sent to reference lab Mon-Sat and resulted within 1-3 days.
Special Instructions:Available stat if urgent.
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.
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: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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