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HelpTest Code VWF von Willebrand Factor Functional, Risto Cofactor (GPIb Binding) Activity
Specimen and Container/Tube
Specimen Type: Plasma
Preferred Specimen: Light Blue Top Tube, 3.2% Sodium Citrate
Other Acceptable specimens: N/A
Specimen Stability
|
Storage Temperature |
Stability |
|
Room temperature |
4 hours |
|
Refrigerated |
not acceptable |
|
Frozen |
30 days |
Collection Instructions
Refer to VWDPKG for collection.
Specimen Handling and Transport Instructions
UCMC Onsite Instructions:
Refer to VWDPKG for collection.
UCMC Offsite and UC MedLab Outreach Instructions:
Refer to VWDPKG for collection.
Rejection Criteria
- Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits.
- Specimens that have wrong ratio of blood to anticoagulant (fill volume), clotted or grossly hemolyzed.
Reference Values
|
Test |
Age |
Sex |
Reference Range |
|
VWF |
ALL |
ALL |
55 - 165% |
Critical Values
|
Analyte |
Unit |
Low |
High |
Age |
|
N/A |
N/A |
N/A |
N/A |
N/A |
Turnaround Time
Turnaround times are relative to the time the specimen is received in the test laboratory.
STAT Turnaround Time: N/A
Routine Turnaround Time: Up to 4 days
Testing Schedule: Twice a week, Monday to Friday, 8 am to 3 pm
Please consult Lab medicine resident on-call (pager 7910) if more rapid test performance is deemed necessary.
Clinical Indications
Diagnosis of von Willebrand disease (VWD)
Test Components
vWF, Risto Cofactor (GPIb Binding) Activity
Methodology
Platelet agglutination
CPT Codes
85245
LOINC Codes
4680-5
Synonyms/Keyword Search
Ristocetin cofactor; vWF activity; von Willebrand Factor
Additional Information
3.2% sodium citrate light blue top tubes must have 9 to 1 ratio of blood to anticoagulant.
Last Review Date
03/05/2025
Volume
Preferred Volume: 2.0 mL
Minimum Volume: 1.0 mL