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
        • May aid in therapeutic decisions
      • 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

Screening

  • Population screening not recommended
  • Screening when other family members have VWD – no specific recommendations but may be considered depending on clinical scenario

Monitoring

  • In patients initially receiving DDAVP
    • Based on therapeutic trial in nonbleeding state after clinical use
    • Measure von Willebrand panel at baseline and 1-2 hours after administering DDAVP (depending on preparation used and desired protocol)
    • Additional 2-4 measurements in patients with previous history of poor response to evaluate for decreased half-life due to rapid clearance
  • After major surgery in patients receiving DDAVP
    • Monitoring with VWF:RCo and FVIII until bleeding risk is reduced
    • Additional post-operative DDAVP based on bleeding and lab values
    • Monitoring of electrolytes if numerous doses of DDAVP given
    • In patients with cardiovascular disease, DDAVP has rarely precipitated myocardial infarction or stroke; consider replacement with VWF concentrates rather than DDAVP in patients with thrombotic risk factors

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 (20% recessive)
    • 2B – autosomal dominant
    • 2M – autosomal dominant
    • 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)
  • Acquired VWD is rare and is associated with other conditions

Clinical Presentation

  • Clinical characteristics of VWD subtypes

    Clinical Characteristics of Subtypes

    Type

    Defect

    Clinical Presentation

    Treatment

    Type 1 – 70-80% of cases

    Partial deficiency of VWF

    Mild mucocutaneous bleeding

    Desmopressin is usually only needed for surgery, dental extractions, childbirth, or injuries

    Type 2 – 15-30% of cases

    • Subtype frequency in the Caucasian population – 2A>2N>2M/2B

    Structurally or functionally abnormal VWF

    Highly variable

    • 2A – mild to moderate mucocutaneous bleeding
      • May have thrombocytopenia
    • 2B – mild to moderate mucocutaneous bleeding
      • Thrombocytopenia may be present
      • Enhanced ability of VWF to bind platelet receptor GP1BA, causes removal of the platelet/VWF complex
    • 2N – symptoms are similar to hemophilia A
    • 2A – Desmopressin therapy may worsen the thrombocytopenia; treatment for severe bleeding episodes may require clotting factor concentrates
    • 2B – Desmopressin therapy may worsen the thrombocytopenia; clotting factor concentrates may be required
    • 2M – Response to desmopressin is usually very poor; may require clotting factor concentrates
    • 2N – Desmopressin for minor bleeding; severe bleeding requires concentrate with both VWF and factor VIII

    Type 3 – rare

    Complete absence of VWF

    Severe mucocutaneous and musculoskeletal bleeding

    Requires clotting factor concentrates containing both VWF and factor VIII

    Platelet-type (PT-VWD or pseudo-VWD)

    Abnormal high-affinity interaction between platelet glycoprotein Ib/V/IX complex and vWF

    Caused by GPIBA mutations

    Often indistinguishable from VWD type 2B

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
Test Name and Number Recommended Use Limitations Follow Up
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Initial testing for suspected bleeding disorder

   
Prothrombin Time 0030215
Method: Electromagnetic Mechanical Clot Detection

Initial testing for suspected bleeding disorder

   
Partial Thromboplastin Time 0030235
Method: Electromagnetic Mechanical Clot Detection

Initial testing for suspected bleeding disorder

   
von Willebrand Panel with Reflex to von Willebrand Multimeric Analysis 2003387
Method: Electrophoresis/Western Blot/Clotting/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination

Recommended panel to subclassify VWD when high suspicion for VWD exists

Contains VWF multimers, factor VIII activity, VWF antigen, and VWF activity (ristocetin cofactor)

Multimeric testing is performed when ristocetin cofactor, VWF antigen, or factor VIII activity is low or if the ratio of ristocetin cofactor to VWF antigen is <0.7

VWF and FVIII are acute phase reactants that may be elevated by stress or illness

Normal values do not exclude VWD

VWF and FVIII values are affected by ABO blood type (lower in blood type O)

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
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

Recommended initial panel for workup of suspected VWD

Panel contains the three recommended tests for the diagnosis of VWD – VWF antigen, VWF activity (ristocetin cofactor), and FVIII activity

von Willebrand Multimeric Panel 0030002
Method: Electrophoresis/Western Blot/Clotting/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination

Not recommended except in cases of high suspicion for VWD

Contains VW multimeric, factor VIII activity, VWF antigen, VWF activity (ristocetin cofactor)

von Willebrand Disease, Platelet Type (GP1BA) 4 Mutations 2005476
Method: Polymerase Chain Reaction/Sequencing/Fragment Analysis

Molecular test to distinguish VWD type 2B from PT-VWD

Clinical sensitivity for type 2B – 80%

Clinical sensitivity for PT-VWD – unknown

von Willebrand Disease, Type 2A (VWF) Sequencing Exon 28 with Reflex to 9 Exons 2005480
Method: Polymerase Chain Reaction/Sequencing

Molecular test to confirm phenotypic diagnosis of VWD type 2A

Clinical sensitivity – 99%

von Willebrand Disease, Type 2B (VWF) Sequencing 2005486
Method: Polymerase Chain Reaction/Sequencing

Molecular test to distinguish VWD type 2B from PT-VWD

Clinical sensitivity – 80%

von Willebrand Disease, Type 2M (VWF) Sequencing 2005490
Method: Polymerase Chain Reaction/Sequencing

Molecular test to confirm a phenotypic diagnosis of VWD type 2M

Clinical sensitivity – 80%

von Willebrand Disease, Type 2N (VWF) Sequencing 2005494
Method: Polymerase Chain Reaction/Sequencing

Molecular test to distinguish VWD type 2N from hemophilia A

Clinical sensitivity – unknown

von Willebrand Modified Panel 0030284
Method: Platelet Agglutination/Microlatex Particle-Mediated Immunoassay

Alternate test for the workup of VWD

Lacks factor VIII activity test

von Willebrand Factor Antigen 0030285
Method: Microlatex Particle-Mediated Immunoassay

Do not use as a standalone test to diagnose VWD

von Willebrand Factor Activity (Ristocetin Cofactor) 0030250
Method: Platelet Agglutination

Do not use as a standalone test to diagnose VWD

Factor VIII, Activity 0030095
Method: Clotting

Alternate test for the workup of VWD

Lacks VWF activity (ristocetin cofactor) test

von Willebrand Factor Multimers 0092281
Method: Qualitative Electrophoresis

Subclassify VWD after initial testing is positive

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