What tests are abnormal in von Willebrand disease (vWD)?

From the Guidelines

In von Willebrand disease (vWD), several laboratory tests would be abnormal, including decreased von Willebrand factor (vWF) antigen levels, reduced vWF activity (ristocetin cofactor activity), and sometimes a prolonged activated partial thromboplastin time (aPTT), as well as abnormalities in VWF multimer analysis, VWF:RCo/VWF:Ag ratio, and factor VIII levels. The most characteristic abnormalities in vWD include:

• Decreased vWF antigen levels
• Reduced vWF activity (ristocetin cofactor activity)
• Prolonged activated partial thromboplastin time (aPTT)
• Abnormalities in VWF multimer analysis
• Low VWF:RCo/VWF:Ag ratio (<0.5-0.7)
• Decreased factor VIII levels These abnormalities reflect the underlying pathophysiology of vWD, which involves deficient or defective vWF, a protein essential for platelet adhesion to damaged blood vessels and for maintaining normal levels of Factor VIII in circulation 1. The pattern and severity of these abnormalities vary depending on the type of vWD, with Type 1 showing mild to moderate reductions in vWF levels and activity, Type 2 demonstrating qualitative defects with variable vWF levels, and Type 3 exhibiting virtually absent vWF 1. Genetic testing can identify specific mutations but is not routinely needed for diagnosis 1. It is essential to consider the clinical context and laboratory results together to diagnose vWD, as some laboratory tests may not be sensitive or specific enough to detect the disease, especially in patients with mild or moderate forms of vWD 1.

From the Research

Abnormal Tests in von Willebrand Disease

The following tests may be abnormal in von Willebrand disease:

• Bleeding time: abnormal in 43% of patients 2
• Activated partial thromboplastin time (aPTT): abnormal in 25% of patients 2
• von Willebrand factor (vWF) activity: abnormal in 79% of patients 2
• vWF antigen: abnormal in 58% of patients 2
• Factor VIII procoagulant (VIII:c): abnormal in 33% of patients 2
• Ristocetin cofactor activity assay: used to confirm diagnosis of vWD 3
• Multimeric analysis of vWF: used to classify vWD into quantitative and qualitative defects 4, 3
• Platelet count: may be normal or abnormal in patients with vWD 4, 2
• Prothrombin time: may be normal or abnormal in patients with vWD, but is not typically used to diagnose vWD 2

Diagnostic Tests

The combination of the following tests can successfully identify 92% of patients with vWD:

• vWF activity
• Bleeding time
• Activated partial thromboplastin time (aPTT) 2 Multimeric analysis of vWF can also contribute to the diagnosis and classification of vWD 3.

Laboratory Testing

Laboratory testing for vWD includes:

• Screening procedures: bleeding time, filter tests, platelet counts, activated partial thromboplastin time (aPTT) 3
• Confirmatory tests: von Willebrand factor (vWF):antigen, vWF:ristocetin cofactor activity assay, vWF:collagen-binding test, ristocetin-induced platelet agglutination, and factor VIII:coagulant activity 3
• Tests for final classification: multimeric analysis, vWF:factor VIII binding, and platelet vWF 3