Geisinger Medical Laboratories Test Catalog

Order Display Name: Geisinger Epic Procedure Code Or ID CPT Code:  

RISTOCETIN COFACTOR ASSAY

Geisinger Epic Procedure Code: LAB3014             Geisinger Epic ID: 7126
       

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/use first 5-10 mL of blood for other purposes.
  • 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
Specimen 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
Frozen -20°C: 30 days
Frozen -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:
 > 40%
CPT code(s):
 85245
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:
 von Willebrand Factor activity
Methodology:
Platelet Aggregation/Agglutination
Synonyms:
Von Willebrand Factor Activity Assay, RICO, Clotting, VIII, VW, Vonwillebrand
VWF activity
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 leads to mucocutaneous bleeding and menorrhagia. Low VWF levels can be observed in acquired or congenital von Willebrand disease (VWD)

Ristocetin cofactor assay (VWF:RCo) is one type of test used to assess for VWD. It assesses the ability of the patients VWF to agglutinate reagent platelets. 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: 03/31/2023

Performing Locations

Geisinger Medical Center

Performing laboratory: Coagulation
Technical Lead: Margaret Knowles-Tuchman
Frequency: Once weekly, first shift
Performed STAT? No
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