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von Willebrand Factor Activity
MessagePerformed in the Hematology Laboratory x5475, 76. Performed as part of the VWSCR panel (vonWillebrand screen)
Test Code
VWACT
CPT Codes
85245
Preferred Specimen
plasma
Minimum Volume
2.7 mL. Sample MUST be drawn to minimum fill line on tube or the sample will be rejected as QNS.
Instructions
If drawn with other coagulation assays: for up to 3 tests draw2, 2.7mL sodium citrate tubes. For 4 or more coagulation tests, draw 3, 2.7 mL sodium citrate tubes.
Transport Container
Light Blue Top (Sodium Citrate), 2.7 mL draw tubes
Transport Temperature
Room temperature
Specimen Stability
Refrigerator Stability: 4 hours
Plasma is stable for 6 months frozen at -70 degrees C.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis, QNS, Clotted
Methodology
Latex agglutination
Setup Schedule
2-3x/week, weekdays between 8-4pm. Plasma is frozen until testing is performed. Special arrangements for STAT/after hours testing can be made by calling the Hematology laboratory at x5475.
Limitations
VWF is an acute-phase reactant and stres, pregnancy, and other situations affect its plasma concentration.
Results are not affected by hemoglobin up to 70 mg/dL, bilirubin up to 4.2 mg/dL, triglycerides up to 1020 mg/dL, and rheumatoid factor up to 200 IU/mL.
Results are not affected by hemoglobin up to 70 mg/dL, bilirubin up to 4.2 mg/dL, triglycerides up to 1020 mg/dL, and rheumatoid factor up to 200 IU/mL.
Reference Range
See interpretive comments. Reference ranges are ABO blood group dependent.
Clinical Significance
To screen for VonWillebrand disease; differentiate VWD from hemophilia; monitor treatment
