Who can perform von Willebrand disease (VWD) testing?

Who Can Perform von Willebrand Disease Testing

Von Willebrand disease testing can be performed in general hemostasis laboratories for initial screening tests (VWF:Ag, VWF:RCo, and FVIII), but specialized VWD assays and definitive subtyping require referral to specialized hemostasis laboratories with expertise in complex VWF testing. 1

Initial Testing Capabilities

General Hemostasis Laboratories

• Most hospital-based hemostasis laboratories can perform the three core initial VWD screening tests: VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), and factor VIII coagulant activity (FVIII), which are grade B recommendations for initial evaluation 1, 2
• Basic coagulation screening tests (CBC, PT, PTT) can be performed in any clinical laboratory with standard hemostasis testing capabilities 1, 3
• Many hemostasis laboratories now have access to automated tests that measure VWF antigen levels and platelet-dependent activity 4

Specialized Testing Requirements

Reference Laboratories and Hemostasis Centers

• VWF multimer analysis is technically complex, requires qualitative interpretation, and should only be performed in specialized laboratories where this testing is performed routinely 1, 4
• Specialized VWD assays including collagen binding assays (VWF:CB), ristocetin-induced platelet agglutination (RIPA), FVIII binding assays, platelet VWF studies, and DNA sequencing of the VWF gene require referral to specialized centers 1, 5
• The differential diagnosis of VWD subtypes (type 1, 2A, 2B, 2M, 2N, or 3) is a prerogative of specialized laboratories where specific tests are performed routinely 4

When to Refer for Specialized Testing

Indications for Hemostasis Specialist Consultation

• Referral to a hemostasis specialist is appropriate for help in interpretation, repeated testing, and specialized VWD studies when initial test results show abnormalities 1
• If one or more initial VWD test results are abnormally low and/or if the ratio of VWF:RCo to VWF:Ag is abnormally low (below 0.5-0.7), specialized testing should be considered 1, 2
• Patients with abnormal initial test results require consultation with a hemostasis specialist for further evaluation and management 2

Critical Laboratory Quality Considerations

Technical Requirements

• Laboratory testing quality varies considerably among laboratories (high interlaboratory coefficient of variation), particularly for VWF:RCo assay which has coefficients of variation of 10-30% 1
• Calibrators for VWF:Ag, VWF:RCo, and FVIII assays should be referenced to the World Health Organization (WHO) plasma standard 1
• Proper sample handling is essential: blood samples must be transported at room temperature, plasma separated promptly, and if not tested within 2 hours, frozen at or below -40°C 1, 2

Common Pitfalls to Avoid

Testing Limitations

• No single laboratory test can screen for all forms of von Willebrand disease, requiring a comprehensive panel approach 2, 6
• Ordering VWF multimer analysis as part of initial screening is inappropriate—this complex test should be reserved for reflex testing when initial results are abnormal 2
• Patient conditions such as stress, exercise, inflammation, pregnancy, or estrogen therapy can falsely elevate VWF levels, and blood group O individuals have 25% lower baseline VWF levels 1, 2
• Atraumatic blood draw is essential to limit tissue factor exposure and minimize falsely high or low values 1