von Willebrand Disease

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
  - 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
  - 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
  - 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 affecting the results of laboratory tests
- vWF values fluctuate over time; if clinical suspicion is high and values are normal, repeat testing may be required for diagnosis
- 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

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

In patients initially receiving DDAVP
- Based on therapeutic trial in nonbleeding state after clinical use
- Measure vW 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

von Willebrand disease (vWD) is the most common congenital bleeding disorder. vWD may result from either a quantitative (types 1 and 3) or a 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

Tests generally appear in the order most useful for common clinical situations

Test name: CBC with Platelet Count & Automated Differential

ARUP #: 0040003

Methodology: Automated Cell Count with Flow Cell Differential

Use:

Initial testing for suspected bleeding disorder

Test name: Prothrombin Time

ARUP #: 0030215

Methodology: Electromagnetic Mechanical Clot Detection

Use:

Initial testing for suspected bleeding disorder

Test name: Partial Thromboplastin Time

ARUP #: 0030235

Methodology: Electromagnetic Mechanical Clot Detection

Use:

Initial testing for suspected bleeding disorder

Test name: Fibrinogen

ARUP #: 0030130

Methodology: Electromagnetic Mechanical Clot Detection

Use:

Initial testing for suspected bleeding disorder

Test name: Thrombin Time with Reflex to Thrombin Time 1:1 Mix

ARUP #: 0030260

Methodology: Clotting

Use:

Initial testing for suspected bleeding disorder

Test name: von Willebrand Panel with Reflex to von Willebrand Multimeric Analysis

ARUP #: 2003387

Methodology: Electrophoresis/Western Blot/Clotting/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination

Use:

Order for patients with suspected vWD based on clinical findings and initial laboratory evaluation

Panel includes vWF antigen, ristocetin cofactor activity, and FVIII activity and reflexes to multimeric analysis if abnormalities are identified

Limitations:

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

Normal values do not exclude vWD

vWF and FVIII are acute phase reactants that may be elevated in times of stress or illness

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

Test name: Bleeding Disorders (Common)

ARUP #: 2003417

Methodology: Microlatex Particle-Mediated Immunoassay, Platelet Agglutination, Electromagnetic Mechanical Clot Detection

Use:

Initial testing for suspected bleeding disorder

Additional Tests Available

Test name: von Willebrand Panel

ARUP #: 0030125

Methodology: Clotting/Platelet Agglutination/Microlatex Particle-Mediated Immunoassay

Comments:

Order for patients with suspected vWD based on clinical findings and initial laboratory evaluation

Panel includes vWF antigen, ristocetin cofactor activity and FVIII activity

Test name: von Willebrand Multimeric Panel

ARUP #: 0030002

Methodology: Electrophoresis/Western Blot/Clotting/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination

Comments:

Test name: von Willebrand Disease, Platelet Type (GP1BA) 4 Mutations

ARUP #: 2005476

Methodology: Polymerase Chain Reaction/Sequencing/Fragment Analysis

Comments:

Test name: von Willebrand Disease, Type 2A (VWF) Sequencing Exon 28 with Reflex to 9 Exons

ARUP #: 2005480

Methodology: Polymerase Chain Reaction/Sequencing

Comments:

Test name: von Willebrand Disease, Type 2B (VWF) Sequencing

ARUP #: 2005486

Methodology: Polymerase Chain Reaction/Sequencing

Comments:

Test name: von Willebrand Disease, Type 2M (VWF) Sequencing

ARUP #: 2005490

Methodology: Polymerase Chain Reaction/Sequencing

Comments:

Test name: von Willebrand Disease, Type 2N (VWF) Sequencing

ARUP #: 2005494

Methodology: Polymerase Chain Reaction/Sequencing

Comments:

Test name: von Willebrand Modified Panel

ARUP #: 0030284

Methodology: Platelet Agglutination/Microlatex Particle-Mediated Immunoassay (LIA)

Comments:

Test name: von Willebrand Factor Antigen

ARUP #: 0030285

Methodology: Microlatex Particle-Mediated Immunoassay

Comments:

Test name: von Willebrand Factor Activity (Ristocetin Cofactor)

ARUP #: 0030250

Methodology: Platelet Agglutination

Comments:

Test name: Factor VIII, Activity

ARUP #: 0030095

Methodology: Clotting

Comments:

Test name: von Willebrand Factor Multimers

ARUP #: 0092281

Methodology: Qualitative Electrophoresis

Comments:

Test name: Ristocetin-Induced Platelet Aggregation

ARUP #: 2003382

Methodology: Qualitative Aggregation

Comments:

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

Guidelines

General

ARUP Institute for Clinical and Experimental Pathology®

Flanders MM, Crist RA, Roberts WL, Rodgers GM. Pediatric reference intervals for seven common coagulation assays. Clin Chem. 2005; 51 (9) :1738-1742.PubMed

Comprehensive Review: April 2011
Last Update: November 2011

Functional Platelet Disorders

Hemophilia