von Willebrand Disease - VWD

Diagnosis

Indications for Testing

• Initial evaluation (personal/family history and physical examination) suggestive of a bleeding disorder
• Important to evaluate other potential causes of mucocutaneous bleeding
  • Disorders of the liver, kidneys, blood, or bone marrow
  • Undiagnosed thrombocytopenia (types 2B and PT-VWD may have thrombocytopenia)
  • Anti-platelet medications (aspirin, NSAIDs, clopidogrel, others)

Laboratory Testing

• Initial evaluation for a bleeding disorder (to exclude other coagulation defects)
  • CBC with platelet count, prothrombin time/partial thromboplastin time (PT/PTT), fibrinogen, or thrombin time (TT)
• In the presence of a strong history of mucocutaneous bleeding, tests for VWD could be considered as part of the initial evaluation
• VWD may prolong the PTT due to its role as a carrier for factor VIII
  • PTT is often normal in VWD
  • If screening PTT is abnormal, PTT mixing studies may be useful in the initial evaluation to differentiate factor deficiency from inhibitor as the cause of the prolonged PTT
    • In VWD, decreased factor VIII may result in a prolonged PTT that demonstrates correction in a mixing study (factor deficiency pattern)
  • VWD type 2B and platelet type may have thrombocytopenia
• von Willebrand panel testing (abnormalities depend on the subtype)
• Initial VWD testing
  • VWF antigen (VWF:Ag) – measures the amount of protein
  • VWF Ristocetin cofactor activity (VWF:Rco) – measures the function of the protein
  • Factor VIII activity
    • Factor VIII is often decreased in VWD because VWF is a carrier for factor VIII
• Multimeric analysis shows the distribution of different-sized multimers and is used for subtyping, typically after initial diagnosis
  • Not recommended for initial screening except in suspected cases of acquired VWD
    • Multimeric abnormalities may be the only abnormality identified in some cases of acquired VWD
  • Types 2A, 2B, platelet type, and many acquired cases have abnormal multimeric distributions
    • Abnormal result defined as absence of high- and/or intermediate-molecular weight multimers (HMW, IMW)
• Additional specialized testing may be necessary for diagnosis and/or subtyping
  • VWF:Rco to VWF:Ag ratio
    • VWD types 2A, 2B, platelet type, and 2M characteristically have lower levels of VWF:Rco compared to VWF:Ag, resulting in a decreased VWF:Rco-to-VWF:Ag ratio
      • Ratios <0.7 or <0.6 suggest one of these qualitative subtypes
  • Ristocetin-induced platelet aggregation (RIPA)
    • RIPA is not considered first-line testing for VWD and is not sensitive to mild forms of VWD (most type 1 cases)
    • RIPA is typically used to confirm and distinguish between type 2 subtypes (2A, 2B/platelet type)
      • Low-dose RIPA detects abnormally increased aggregation seen in type 2B and platelet-type VWD
  • vWF:platelet binding
    • Detects abnormally increased platelet binding seen in type 2B
    • Differentiates type 2B from platelet-type VWD (test is normal in platelet type)
  • VWF:FVIII binding
    • Differentiates between type 2N and hemophilia A (test is normal in hemophilia A)
  • Genetic/molecular testing may be useful for the following
    • Confirm phenotypic diagnosis of VWD type 2A, 2B, 2M, 2N, or platelet-type
    • Distinguish VWD type 2B from platelet-type VWD
    • Distinguish VWD type 2N from hemophilia A
    • Evaluate family members of individuals with known mutations
  • Classification of VWD type
• Expected laboratory values in VWD by subtype

  Expected Laboratory Values in VWD by Subtype
  Type and Frequency	1 (~80%)	2A (10%)	*2B (<5%)	2M (<2%)	2N (<1%)	3 (rare)
  Test and Values
  VWF:Ag	Decreased	Frequently decreased	Frequently decreased	Frequently decreased	Normal to mildly decreased	Markedly decreased or absent
  VWF:RCo	Decreased	Significantly decreased	Often significantly decreased	Often significantly decreased	Normal to mildly decreased	Markedly decreased or absent
  FVIII	Normal to mildly decreased	Normal to mildly decreased	Normal to mildly decreased	Normal to mildly decreased	Moderately decreased	Markedly decreased (<10)
  Platelet count	Normal	Usually normal	Often slightly low; exacerbated by surgery, stress, pregnancy	Normal	Normal	Normal
  Multimer pattern	Normal	Abnormal; loss of HMW & IMW multimers	Abnormal; loss of HMW multimers	Normal	Normal	Absent
  ** RIPA	Often normal	Reduced aggregation at high ristocetin concentrations	Abnormal; enhanced aggregation at low ristocetin concentrations	Reduced at high ristocetin concentrations	Normal	Absent
  +VWF:VIII binding	Normal	Normal	Normal	Normal	Decreased	NA
  RCo:Ag ratio	Normal (>0.5-0.7)	Decreased (<0.5-0.7)	Decreased or normal (usually <0.5-0.7)	Decreased (<0.5-0.7)	Normal (>0.5-0.7)	NA
  * Similar lab and clinical features also exhibited by platelet-type VWD due to abnormalities in GP1b receptor; use genetic testing or VWF platelet-binding assay (also called type 2B binding) to distinguish ** RIPA must be performed by a local laboratory due to limited sample stability + Measures ability of VWF to bind factor VIII

• Factors that may affect laboratory testing in VWD
  • VWF values fluctuate over time; if clinical suspicion is high and values are normal, repeat testing may be required for diagnosis
  • Initial laboratory testing may be normal in patients with mild disease
  • Mildly decreased VWF values are not diagnostic
  • Both VWF and FVIII are acute phase reactants and may be elevated by stress, illness, or medications, which can mask actual deficiencies
    • Conditions include pregnancy, estrogen-containing medications, inflammation, infection, liver disease, malignancy, exercise, stress/anxiety, and trauma (including traumatic venipuncture)
  • VWF values and FVIII activity are affected by ABO blood type (type O individuals have ~25% lower values than non-ABO individuals)
  • Results for VWF and FVIII testing can be affected by pre-analytical variables such as collection technique, specimen preparation, storage, and transport
    • Cold storage of citrated whole blood prior to centrifugation can markedly reduce VWF and FVIII values and can also induce multimeric abnormalities leading to an incorrect diagnosis of VWD or hemophilia A or incorrect subtyping of VWD

Differential Diagnosis

• Functional platelet disorders
• Hemophilia A or other coagulation factor deficiencies
• Underlying malignancy (cause of acquired VWD)
  • Lymphoproliferative disease
    • B-cell lymphoma
    • T/NK-cell lymphoma
  • Myeloproliferative neoplasms
  • Leukemia
    • Acute myeloid leukemia
    • Acute lymphoblastic leukemia

Screening

Monitoring

Clinical Background

von Willebrand disease (VWD) is the most common congenital bleeding disorder. VWD may result from either a quantitative (types 1 and 3) or qualitative (type 2) abnormality of von Willebrand factor (VWF).

Epidemiology

• Incidence
  • May be as high as 1/100
  • Frequency of types
    • Type 1 – 70-80%
    • Type 2 – 15-30%
    • Type 3 – rare
• Sex – M:F, equal
• Ethnicity – more common in Caucasians

Genetics

• Type 1 – autosomal dominant with incomplete penetrance (60%)
• Type 2
  • 2A – autosomal dominant (or recessive)
  • 2B – autosomal dominant
  • 2M – autosomal dominant (or recessive)
  • 2N – autosomal recessive
• Type 3 – autosomal recessive
• Platelet-type (PT-VWD) – autosomal dominant
  • Abnormality of the platelet von Willebrand receptor, glycoprotein 1b (GP1b)

Pathophysiology

• VWF is a large multimeric plasma protein that mediates adherence of platelets to the vessel wall at sites of injury; it is also a carrier for factor VIII
• VWD results from either deficiency or dysfunction of VWF and is characterized by type of defect
  • Quantitative
    • Partial deficiency – type 1
    • Complete deficiency – type 3
  • Qualitative – type 2 (2A, 2B, 2M, 2N)
    • 2N – disease resembles hemophilia A
• Acquired VWD is rare and is associated with other conditions
  • Autoantibody formation
    • Lymphoproliferative disease – B-cell lymphoma, T/NK-cell lymphoma, plasma cell dyscrasias
    • Autoimmune disease (eg, systemic lupus erythematosus)
  • Shear-induced proteolysis – structural heart defects (ventricular septal defect, aortic stenosis), pulmonary hypertension
  • Increased platelet binding – conditions with markedly increased platelet counts
    • Myeloproliferative neoplasms
  • Hypothyroidism
  • Medication-induced – valproic acid, ciprofloxacin, griseofulvin

Clinical Presentation

• History of mucocutaneous bleeding (platelet-type bleeding)
  • Epistaxis
  • Menorrhagia in females
  • Excessive bleeding with surgery or dental extractions
  • Easy bruising, ecchymoses
  • Bleeding from minor skin cuts
  • More severe bleeding suggests type 3 or type 2N
    • Hemarthroses
    • Central nervous system bleeding
    • Gastrointestinal bleeding
• Presentation and severity of bleeding are dictated by subtype and specific abnormality present
  • Type 1 – usually mild
  • Type 2 – usually moderate (type 2N can be severe)
  • Type 3 – usually severe

Treatment

• Appropriate treatment is dictated by subtype and clinical presentation
  • Most cases of VWD are mild and may require treatment only with surgery, dental extractions, injury, or childbirth
  • Treatment options may include
    • Mild VWD – desmopressin acetate (DDAVP) to release stored VWF 
    • Moderate to severe VWD – replacement therapy with factor concentrates containing VWF (Humate-P^®, Alphanate FD/HT^®)
  • Acquired VWD – treatment of the underlying disorder is most effective

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Fibrinogen 0030130 Method: Electromagnetic Mechanical Clot Detection	Possible secondary testing for suspected bleeding disorder
Thrombin Time with Reflex to Thrombin Time 1:1 Mix 0030260 Method: Clotting	Possible secondary testing for suspected bleeding disorder
von Willebrand Panel 0030125 Method: Clotting/Platelet Agglutination/Microlatex Particle-Mediated Immunoassay	Order for patients with suspected VWD based on clinical findings and initial laboratory evaluation Panel includes VWF antigen, ristocetin cofactor activity, and FVIII activity
von Willebrand Multimeric Panel 0030002 Method: Electrophoresis/Western Blot/Clotting/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination
von Willebrand Disease, Platelet Type (GP1BA) 4 Mutations 2005476 Method: Polymerase Chain Reaction/Sequencing/Fragment Analysis
von Willebrand Disease, Type 2A (VWF) Sequencing Exon 28 with Reflex to 9 Exons 2005480 Method: Polymerase Chain Reaction/Sequencing
von Willebrand Disease, Type 2B (VWF) Sequencing 2005486 Method: Polymerase Chain Reaction/Sequencing
von Willebrand Disease, Type 2M (VWF) Sequencing 2005490 Method: Polymerase Chain Reaction/Sequencing
von Willebrand Disease, Type 2N (VWF) Sequencing 2005494 Method: Polymerase Chain Reaction/Sequencing
von Willebrand Modified Panel 0030284 Method: Platelet Agglutination/Microlatex Particle-Mediated Immunoassay
von Willebrand Factor Antigen 0030285 Method: Microlatex Particle-Mediated Immunoassay
von Willebrand Factor Activity (Ristocetin Cofactor) 0030250 Method: Platelet Agglutination
Factor VIII, Activity 0030095 Method: Clotting
von Willebrand Factor Multimers 0092281 Method: Qualitative Electrophoresis
Ristocetin-Induced Platelet Aggregation 2003382 Method: Qualitative Aggregation	Typically used to confirm and distinguish between type 2 subtypes (2A, 2B/platelet type) Not considered first-line testing for VWD; not sensitive to mild forms of VWD (most type 1 cases) Available only for local clients due to limited sample stability
von Willebrand Factor Collagen Binding 2007136 Method: Enzyme-Linked Immunosorbent Assay

Diagnostic Algorithm

  von Willebrand Disease Testing Algorithm