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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 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 |
CPT Codes
85245
LOINC Codes
4680-5
Volume
Preferred Volume: 2.0 mL
Minimum Volume: 1.0 mL
Specimen Stability
|
Storage Temperature |
Stability |
|
Room temperature |
4 hours |
|
Refrigerated |
not acceptable |
|
Frozen |
30 days |
Collection Instructions
Refer to VWDPKG for collection.
Test Components
vWF, Risto Cofactor (GPIb Binding) Activity
Clinical Indications
Diagnosis of von Willebrand disease (VWD)
Methodology
Platelet agglutination
Additional Information
3.2% sodium citrate light blue top tubes must have 9 to 1 ratio of blood to anticoagulant.
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.
Synonyms/Keyword Search
Ristocetin cofactor; vWF activity; von Willebrand Factor
Last Review Date
03/05/2025