Ristocetin Cofactor Activity


Abbrev Code:RI   
Order Code:LAB3715Order Name:Ristocetin Cofactor
Synonyms:von Willebrand Factor Ristocetin Cofactor Activity; VWF:Rco; VWF Ristocetin Cofactor Activity; Ristocetin Cofactor Activity; RCF
Methodology:Platelet Agglutination
CPT Codes: 85245 x1, 85245 x1
Turnaround Time:Specimens are sent to the reference laboratory Mon-Sat; results are reported in 1-3 days.
Special Instructions:RCF is the outreach code (Atlas and paper requisition) for Ristocetin Cofactor Activity send out test. DO NOT SEND OUT DIRECTLY TO REFERENCE LAB, SEND TO SPECIAL COAGULATION LAB. Special Coagulation will determine if a ristocetin cofactor activity is required based on the von Willebrand Factor Panel Algorithm or von Willebrand Factor Screen Algorithm prior to sending specimen to ARUP Laboratories for testing. Usually performed as part of a von Willebrand screen or von Willebrand panel. If Special Coagulation Lab determines testing is required, the sample will be returned to Specimen Management for sending to the reference laboratory. See associated links for additional information.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens, von Willebrand Factor (VWF) Panel Algorithm, 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 tube. If part of a von Willebrand panel, collect TWO tubes.
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

Reference Range:
   
Use:To measure the "activity" of von Willebrand factor. Ristocetin was found to cause thrombocytopenia in most patients by inducing platelet aggregation. This platelet aggregation is reduced in patients with von Willebrand's disease. Therefore, the "activity" of von Willebrand antigen can be measured by the rate at which the patient's platelet-poor plasma causes aggregation of stabilized human platelets in the presence of Ristocetin.


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