Ristocetin Cofactor
General Information
HLAB/HOL Code: VW
UPHSM LIS Test #: 023290
Schedule:
Testing Time: 1-3 Days
Testing Lab: LabCorp
UPHSM LIS Test #: 023290
Schedule:
Testing Time: 1-3 Days
Testing Lab: LabCorp
Specimen Info
Only 1 specimen type required, unless otherwise specified
Volume: 1.0 mL
Temperature: Frozen
Tube Type: Platelet Poor Plasma (sodium citrate)
Collection Info:
Collection: Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.
Temperature: Frozen
Tube Type: Platelet Poor Plasma (sodium citrate)
Collection Info:
Collection: Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.
Specimen Acceptability
Cause for Rejection:
Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling
Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling
Methods
In this ristocetin cofactor assay, the patient plasma is mixed with formalin-fixed platelets in the presence of ristocetin.12 The extent of platelet agglutination detected photo-optically is proportional to the vWF activity of the sample.
Clinical Utilities
Screen and diagnose von Willebrand factor (vWF) deficiency6,8-10
CPT Codes
85245
* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding
is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.
