Reflex criteria:

Decrease in the VWF:Act and/or the VWF:Agn results will automatically reflex to von Willebrand multimers (CIEP), referred to LabCorp, at an additional charge.

HemosIL von Willebrands Factor activity assay is an antibody-based assay (vWF:Ab) that uses specific anti-VWF monoclonal antibody directed against the platelet-binding site of VWF (glycoprotein Ib receptor) adsorbed onto latex reagent particles which react with the VWF of patient plasma. The degree of agglutination is directly proportional to the activity of VWF in the sample. The clinical sensitivity of the vWF:Ab assay is similar to aggregometry based vWF:RCo (Ristocetin cofactor) assays in screening for congenital vWD and has an apparently improved sensitivity for acquired von Willebrand’s syndrome (AVWS).  Additional evaluation including multimer testing is necessary for subclassification of vWD types.

Lt blue Sodium citrate (Na Cit) - 2.7mL  x 4

If the patient has a hematocrit >55, a specially prepared Lt blue Sodium citrate (NaCit) tube must be used in place of the standard Lt blue Sodium citrate (NaCit) tube.

Hematocrit-Anticoagulant adjustments

• Do not over or under fill tube as the ratio of anticoagulant to whole blood is critical

Coag – tube fill guidelines

• Immediatley following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting

• Process Platelet Poor Plasma (P.P.P)
  • Coag – how to prepare a specimen for special coagulation testing
• Transfer plasma into a Microcentrifuge vial/tube (Beaker sites) or Coagulation specimen transport vial/tube (all other sites), labeled as platelet poor plasma
• Freeze immediately, or within two (2) hours of sample collection

Microcentrifuge vial/tube in a Snap cap conical vial/tube and cap (Beaker sites)

Coagulation specimen transport vial/tube  (all other sites)

Frozen - strict

Multimer samples are stabile for 14 days at -70°.

Refrigerated - NO

• Samples collected in Greiner tubes
• Improper labeling (unlabeled or mislabeled)
• Improper anticoagulant
• Improperly filled (over or underfilled) tube
• Hemolysis
• Clotted specimen
• Delay in transport
• Improper storage/transport temperature
• Patient on heparin > 1.0 IU/mL.

vWF:Act - Immunoturbidimetry

VWF:Ag - Immunoturbidimetry

FVIII: Clotting

Von Willebrand factor activity levels are blood group specific with individuals of 'O' blood type showing lower von Willebrand activity levels than other blood groups.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. Clinically, it is often characterized by mucocutaneous hemorrhages. The three principle types of VWD are:

• Type 1 corresponds to a quantitative deficiency of VWF; its transmission is autosomal dominant and is the most frequently encountered (70 – 80%).
• Type 2 refers to a qualitative deficiency of VWF; the defect is often located in the multimeric structure. Its transmission is autosomal dominant or recessive.
• Type 3 is characterized by a total absence of VWF in both the plasma and cellular components. Its transmission is autosomal recessive.

Acquired VWF deficiencies may be associated with several clinical states such as in myeloma, lymphoma, systemic lupus erythematosus, hypothyroidism, etc. These cases may be referred to as acquired von Willebrand diseases.
VWF is a protein involved in inflammation. Its level increases when there are damages of the vascular endothelium (post-operative period, infection, cancers, renal or hepatic disorders). Some authors have noted that high vWF levels are encountered during cardiovascular disorders, notably during some types of myocardial infarction.

Acquired von Willebrand Syndrome has been reported rarely with the use of griseofulvin, ciprofloxacin, tetracycline, thrombolytic agents and hydroxyethyl starch.