One 4.5 mL light blue top tube (sodium citrate). Collect by careful venipuncture to avoid tissue fluid contamination or hemolysis. Do not use needles smaller than 23 gauge. Fill tube to maximum draw, at least 3/4 full. Mix by gentle inversion. Call the Special Coagulation Department (541-687-2134 x4612) when urgent testing is needed in order to assure STAT testing.
Handling:
Due to short stability, specimen must either be sent STAT to arrive in laboratory within 4 hours, or send frozen. For STAT, refrigerate and keep capped in original tube. Call for STAT pick-up. For standard delivery, centrifuge to produce platelet poor plasma (at least 1700 G for 15 minutes) and using a plastic pipette, transfer plasma into a plastic vial. Label with patient name, I.D. number, test, and “citrated plasma” and freeze immediately. Send to the laboratory within 7 days. If multiple tests are ordered, freeze a separate aliquot for this test.
Stability:
4 hours refrigerated, or 7 days frozen. Unstable ambient.
Standard Volume:
5 mL whole blood, or 2 mL plasma.
Minimum Volume:
1.8 mLwhole blood, or 0.5 mL plasma.
Transport:
Original tube refrigerated if STAT, or citrated plasma frozen on dry ice in a Styrofoam container.
Comments:
Von Willebrand Factor is an ”acute phase reactant.” As a result, the VWF level increases during pregnancy, infection, and inflammation. Patients should not be screened for Von Willebrand disease during these conditions, since abnormal results may transiently normalize and mask disease. See also: Coagulation Study, von Willebrand Disease (25770).
Rejection Criteria:
Clotted specimen; serum; gross hemolysis; specimen received in laboratory beyone stated stability.
Reference Range:
VWF Ag reference ranges vary with blood type, with lower values observed in normal individuals of blood type O.
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