Performance Evaluation of Von Willebrand:Collagen-Binding Assays to Diagnose Von Willebrand Factor Deficiency in Patients With Increased Risk of Bleeding

Study Overview
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Brief Summary
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Von Willebrand Disease (VWD) is defined as an inherited bleeding disorder that is caused by deficiency or dysfunction of von Willebrand factor (VWF), a plasma protein that mediates the initial adhesion of platelets at sites of vascular injury and also binds and stabilizes blood clotting factor VIII (FVIII) in the circulation. The most severe forms of VWD are usually easy to diagnose (obvious hemorrhagic symptoms and major VWF deficiency), whereas the mild forms of the disease are still difficult to confirm. It is indeed reported that about 1% of the population carry mild biological VWF deficiency without any bleeding tendency and any actual disease. On the contrary, some patients with severe bleeding history can carry a true VWF abnormality, well-confirmed by genetic studies, without any VWF deficiency when evaluated with standard biological methods, such as Ristocetin Cofactor activity (VWF:RCo). However, in these patients, the use of alternative methods, such as PFA-100 (Platelet Fonction Analyzer-100), the study of Factor VIII (FVIII:C) to VWF (FVIII:C/VWF) ratio or the evaluation of VWF activity using more specialized methods such as VWF:CB (VWF-Collagen Binding) assay can detect the VWF deficiency and possible hemorrhagic predisposition. In this project, the investigators plan to assess the performance of VWF:CB in the diagnosis of VWF deficiency in patients with unexplained bleeding history.

Official Title
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Performance Evaluation of Von Willebrand:Collagen-Binding Assays to Diagnose Von Willebrand Factor Deficiency in Patients With Increased Risk of Bleeding

Conditions
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Von Willebrand Disease

Intervention / Treatment
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* Other: Non interventional study


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patient with bleeding history sent to the Hemophilia Treatment Center in Dijon or Nantes University Hospital with abnormal bleeding score (>3 in men and >5 in women Patient who has provided a signed consent to participate at this study and for blood sampling Affiliation with French social security system Non-Inclusion Criteria: Minors will not be included in the study. On-going pregnancy and postpartum period (3 months after delivery) Substitutive treatment with coagulation factor concentrates or desmopressin administration within 10 days before sampling. Ongoing infectious or inflammatory disease that can modify VWF levels. Diagnosis of obvious hemostasis disorder

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Non interventional study|no intervention|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Von Willebrand factor levels measured with Von Willebrand factor: Collagen-Binding methods | Deficiency is defined when VWF level is < 50IU/dL, as usually defined by Favaloro E.J. (2000). A composite reference standard (CRS) will be used to improve the imperfect Gold Standard (VWF: RCo). CRS will be defined as being positive if either VWF: RCo, VWF:Ag, PFA-100 or FVIII:C will be positive and negative otherwise. | Up to 1 year | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Willebrand factor deficiency, hematology, Willebrand:Collagen-binding