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Lab Dept:
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Coagulation
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Test Name:
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VON WILLEBRAND ANTIGEN
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General Information
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Lab Order Codes:
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VONAM
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Synonyms:
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Factor VIIIR:Ag; Factor VIII Related Antigen; VIIIR Antigen; vWF Ag; Factor VIII Activity; von Willebrand Factor Immunodeficiency Assay
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CPT Codes:
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85246 – Factor VIII vW antigen factor
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Test Includes:
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Von Willebrand antigen reported as a %.
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Logistics
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Test Indications:
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Useful for diagnosis (or exclusion) of von Willebrand’s disease or trait.
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Lab Testing Section:
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Coagulation (Minneapolis Campus)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Twice Weekly (Tuesday and Friday)
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Turnaround Time:
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3 – 5 Days
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Special Instructions:
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See Patient Prepartion
Deliver immediately to the laboratory at room temperature. Indicate when specimen is drawn from a line or a heparin lock.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Light Blue (Buffered Na Citrate 3.2%) top tube
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Draw Volume:
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2.7 mL blood
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Processed Volume:
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0.9 mL plasma
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Collection:
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● A clean venipuncture is essential.
● If the patient’s hematocrit is >55%, call the laboratory for a special tube. Fill tube completely.
● Mix thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: All testing will be performed in Minneapolis.
St. Paul Lab: Send whole blood specimens to Mpls for processing via courier. Must be processed within 4 hours of collection. Contact Mpls prior to sending.
Mpls Lab: Spin sample collected in blue top tube for 5 minutes on the Stat Spin centrifuge, remove plasma and transfer to a 4 mL BCS sample cup. Spin remaining plasma again for 5 minutes in the Stat Spin Centrifuge. Transfer plasma to a new BCS sample cup for analysis leaving approximately 200 mcL in the bottom of the original cup to discard.
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Patient Preparation:
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No Heparin for 2 days prior to testing.
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Sample Rejection:
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Clotted sample; underfilled tube; mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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Age:
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Range (%):
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Full Term Infants
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Day 1
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50 – 207%
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Day 5
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50 – 254%
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Day 30
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50 – 246%
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Day 90
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50 – 206%
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Day 180
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50 – 197%
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Childhood
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1 – 5 years
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60 – 120%
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6 – 10 years
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44 – 144%
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11 – 16 years
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46 – 153%
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Adult
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50 – 158%
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Critical Values:
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N/A
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Limitations:
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This test measures the quantity of von Willebrand von Willebrand Antigen, factor protein not functional activity. Antigen and activity values are increased in patients who are pregnant or are taking oral contraceptives.
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Methodology:
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Measurement of vonWillebrand’s factor protein i.e., antigen by the immuno-turbimetric method. Patient dilutions are compared to a known set of standard dilutions and a percentage is determined.
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References:
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Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis
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Updates:
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5/24/2010: Tubing patient specimens is no longer prohibited.
12/14/2010: Updated processing information.
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