von Willebrand Factor Multimer Analysis
MAYO: VWFM2, EPIC: LAB6184, SOFT: XVWAM
A copy of Ristocetin Cofactor, von Willebrand Facter Antigen, and Factor VIII Activity are required to be sent with the specimen. Multimer analysis will only be performed when Ristocetin Cofactor or von Willebrand Factor Antigen are below normal.
Specimen Collection Criteria
Collect: Two Light Blue-top Sodium Citrate tubes.
TUBES MUST BE FULL.
Physician Office/Drawsite Specimen Preparation
For optimal results, maintain whole blood specimen at room temperature (20-26°C or 68-78.8°F) prior to transport. Transport whole blood to the Laboratory within 4 hours of collection. If transport within 4 hours is not possible, the following procedure must be followed for accurate results:
- Centrifuge the capped tubes at 1500 x g for 15 minutes.
- Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
- Immediately remove only the top two-thirds of the PPP and transfer into a plastic tube.
- Freeze (-20°C/-4°F or below) the PPP immediately.
- Transport frozen on DRY ICE. Specimen must remain frozen during transport.
Preparation for Courier Transport
Transport: 1.0 mL PPP in two 0.5 mL aliquots, frozen (-20°C/-4°F or below).
- Grossly hemolyzed specimens.
- Grossly iceteric specimens.
- Grossly lipemic specimens.
- Specimens not collected and processed as indicated.
Specimen Stability for Testing:
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): 42 days
Specimen Storage in Department Prior to Disposal:
Specimen retention time is determined by the policy of the reference laboratory. Contact the Sendout Laboratory with any questions.
Sent to Mayo Medical Laboratories, Rochester, MN.
Monday - Wednesday.
Results available in 8-11 days.
Agarose Gel Electrophoresis/Infrared Dye-Labeled Antibody Detection.
The plasma vWF multimer analysis is a qualitative visual assessment of the size spectrum and the banding pattern of vWF multimers.
This test is used to identify variants of vWD that have few of the larger multimers, have unusually large multimers, or have qualitatively abnormal "bands" that indicate an abnormal vWF structure.
vWF multimer analysis is not useful if:
- the following tests are NOT abnormally low - Coagulation Factor VIII Activity Assay, Ristocetin Cofactor, or von Willebrand Factor Antigen.
- the vWF ristocetin cofactor to vWF antigen ratio is greater than or equal to 0.8.
This assay is used to detect variant forms of von Willebrand disease (vWD) with abnormal molecular weight multimers. Von Willibrand factor (vWF) is a protein that is important in platelet adhesion to subendothelial tissues. Decreased levels or abnormal multimerization are associated with mucocutaneous bleeding.
von Willebrand factor (vWF) is a large multimeric plasma glycoprotein that performs 2 critical functions in hemostasis:
- vWF is a ligand and mediates platelet adhesion to the subendothelial matrix at the site of vessel wall injury by binding to the constitutively active platelet receptor glycoprotein (GP)-Ib/V/IX complex, and to subendothelial matrix collagen, and;
- vWF is a carrier molecule for procoagulant factor VIII in the circulation, increasing the factor VIII half-life five-fold. Under conditions of high shear, vWF also mediates platelet-platelet cohesion by binding to the platelet receptor GP-IIb/IIIa (integrin alpha IIb beta3).
A bleeding disorder, von Willebrand disease (vWD), occurs when vWF is quantitatively deficient or qualitatively abnormal. vWD manifests clinically as easy bruising, mucocutaneous bleeding (e.g., epistaxis, menorrhagia), and bleeding after trauma or surgery. vWD is the most common of the inherited bleeding disorders, and can also occur on an acquired basis.
Plasma vWF consists of a series of multimers varying in size from dimers to multimers over 40 subunits (greater than 10 million Daltons). The largest multimers provide multiple binding sites that can interact with both platelet receptors and subendothelial matrix sites of injury, and are the most hemostatically active form of vWF.
Inherited vWD has been classified into 3 types:
- Type 1, typically an autosomal dominant disease, is the most common, accounting for approximately 70% of vWD patients. It represents a quantitative deficiency of vWF of variable severity.
- Type 2, which is usually an autosomal dominant disease, is characterized by several qualitative abnormalities of vFW. Four subtypes have been identified: 2A, 2B, 2M, and 2N.
- Type 3, an autosomal recessive disorder, leads to severe disease with extremely reduced or undetectable levels of vWF, as well as very low factor VIII.
Acquired von Willebrand syndrome (AVWS) is associated with a number of different disease states and is caused by several different pathophysiological mechanisms, including antibody formation, proteolysis, binding to tumor cells with increased clearance, and decreased synthesis. AVWS is most frequently described in patients with dysproteinemias (including MGUS [monoclonal gammopathy of undetermined significance], multiple myeloma, and macroglobulinemia), lymphoproliferative disorders, myeloproliferative disorders (e.g., essential thrombocythemia), autoimmune diseases (e.g., systemic lupus erythematosus [SLE]), severe aortic stenosis, gastrointestinal angiodysplasia, and hypothyroidism.
Subtyping of vWD:
- When results of complementary laboratory tests (Coagulation Factor VIII Activity Assay, Ristocetin Cofactor, von Willebrand Factor Antigen) are abnormally low or discordant.
- This test is primarily used to identify variants of type 2vWD.
- As an aid in determining appropriate treatment.
MAYO: VWFM2, EPIC: LAB6184, SOFT: XVWAM