IX international curse of continuing formation in haemophilia and other congenital coagulopathies. The role of the Laboratory in coagulation disorders. Diagnosis of von Willebrand disease.

Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (VWF). This protein far from simplicity constitutes a very complex molecular model, remaining unravelled yet many aspects of it, even though the VWF gene (VWF) was cloned already in 1985 and the structure of VWF well defined. VWD diagnosis is difficult to achieve in a significant proportion of patients due to both disease heterogeneity and limitations in existing test processes. The cornerstone of diagnosis relies on interpretation of VWF test results, the presence of clinical manifestations of bleeding, especially mucocutaneous, and (in most cases) a positive family history. However, even with a significant bleeding history, a family history may not be positive due to factors of incomplete penetrance and variable expressivity that affect genetic changes. The laboratory diagnosis of VWD can be difficult, as the disease is heterogeneous and an array of assays is required to describe the phenotype. Basic classification of quantitative (type 1 and 3) and qualitative (type 2 variants) VWD requires determination of VWF antigenic (VWF:Ag) levels and assaying of VWF ristocetin cofactor (VWF:RCo) activity. The latter is required for identifying and subtyping VWD, but the assay is poorly standardized. For that reason, novel VWF activity assays have been developed awaiting more extensive comparison data between different methodologies and requiring validation on larger patient series. The qualitative type 2 VWF deficiency can be further divided into four different subtypes (A, B, M and N) using specific assays that measure other activities or the size distribution of VWF multimers. However, frequently, it may be difficult to correctly classify the VWD phenotype, and genetic analysis is through mutation identification may provide a tool to clarify the disorder.

Type 2N VWD: Conclusions from the Spanish PCM-EVW-ES project.

INTRODUCTION: Type 2N von Willebrand disease (VWD) is characterized by a decreased affinity of von Willebrand factor (VWF) for factor VIII (FVIII). Abnormal binding of FVIII to VWF (VWF:FVIIIB), results in low FVIII plasma levels, which can lead to a misdiagnosis of mild haemophilia A. Accurate diagnosis of type 2N VWD is essential for appropriate genetic counselling and therapy. This disease can be distinguished from haemophilia A by in vitro assays (measurement VWF:FVIIIB activity) and/or genetic analysis. AIM: To identify the current challenges in the diagnosis and treatment of this type of VWD and provide an in-depth description of the phenotypes and mutations identified. RESULTS: Twenty-eight patients had at least one type 2N mutation, and 13 of these had a type 2N mutation combined with other variations. Three type 2N mutations were detected: p.Arg816Trp, p.Arg854Gln, and p.Arg763Ser. Two of these are the most frequently described mutations worldwide. This mutational spectrum differs from the broad spectrum seen in neighbouring France, where at least eight distinct 2N mutations have been found. In the PCM-EVW-ES cohort, 11 asymptomatic type 2N carriers with borderline FVIII plasma levels would probably have been excluded if the evaluation had been based on clinical and laboratory data only. Likewise, three patients with a severe phenotype would have been classified as homozygous for a 2N mutation if only the phenotype study had been performed. CONCLUSION: The high detection yield and affordability of next-generation sequencing support the use of this technology as a first-line diagnostic tool in this setting.

Unraveling the Influence of Common von Willebrand factor variants on von Willebrand Disease Phenotype: An Exploratory Study on the Molecular and Clinical Profile of von Willebrand Disease in Spain Cohort.

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the "Molecular and Clinical Profile of von Willebrand Disease in Spain project." To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

Update on Molecular Testing in von Willebrand Disease.

Diagnosis of von Willebrand disease (VWD) depends on personal and family history of bleeding and confirmatory laboratory testing. Currently available phenotypic tests for VWD contain potential sources for error that may distort results. Despite an exponential growth of information about the von Willebrand factor gene (VWF), the role of molecular diagnosis in VWD is still controversial. Due to the complexity and high cost of conventional molecular analyses, some investigators have recommended limiting this approach to distinguish suspected type 2N VWD from hemophilia A, type 2B from platelet-type VWD, and the exploration of type 3 VWD. New genetic methodologies and approaches are becoming available, but there is still some reluctance for their implementation in VWD diagnosis. This article discusses the pros and cons of molecular testing in VWD considering the experience obtained through the multicenter project "Molecular and Clinical Profile of VWD in Spain (PCM-EVW-ES)."

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA.

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Role of multimeric analysis of von Willebrand factor (VWF) in von Willebrand disease (VWD) diagnosis: Lessons from the PCM-EVW-ES Spanish project.

The multimeric analysis (MA) of plasma von Willebrand factor (VWF) evaluates structural integrity and helps in the diagnosis of von Willebrand disease (VWD). This assay is a matter of controversy, being considered by some investigators cumbersome and only slightly informative. The centralised study 'Molecular and Clinical Profile of von Willebrand Disease in Spain (PCM-EVW-ES)' has been carried out by including the phenotypic assessment and the genetic analysis by next generation sequencing (NGS) of the VWF gene (VWF). The aim of the present study was to evaluate the role of MA to the diagnosis of these patients and their potential discrepancies. Two hundred and seventy out of 480 patients centrally diagnosed with VWD had normal multimers, 168 had abnormal multimers and 42 a total absence of multimers. VWF MA was of great significance in the diagnosis of 83 patients (17.3%), it was also of help in the diagnosis achieved in 365 additional patients (76%) and was not informative in 32 cases (6.7%). With regard to discrepancies, 110 out of 480 (23%) patients centrally diagnosed with VWD presented some kind of discordance between VWF:RCo/VWF:Ag and/or VWF:CB/VWF:Ag ratios, multimeric study and/or genetic results. The VWF MA was key in the presence of novel mutations as well as in cases with phenotypic discrepancies. A comparison between the contribution of MA and VWF:CB showed a clearly higher contribution of the former in the diagnostic process. These data seem to reinforce the relevance of the VWF MA in VWD diagnosis, despite all its limitations.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): comprehensive genetic analysis by next-generation sequencing of 480 patients.

Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): Proposal for a new diagnostic paradigm.

The diagnosis of von Willebrand disease (VWD) remains difficult in a significant proportion of patients. A Spanish multicentre study investigated a cohort of 556 patients from 330 families who were analysed centrally. VWD was confirmed in 480. Next generation sequencing (NGS) of the whole coding VWF was carried out in all recruited patients, compared with the phenotype, and a final diagnosis established. A total of 238 different VWF mutations were found, 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 463 were found to have VWF mutation/s. A good phenotypic/genotypic association was estimated in 96.5% of the patients. One hundred seventy-four patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred sixteen patients presented with mutations that had previously been associated with increased von Willebrand factor (VWF) clearance. RIPA unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 70 patients. The NGS study facilitated an appropriate classification in 63 of them. The remaining seven patients presented with a VWF novel mutation pending further investigation. In five patients with a type 3 and two with a type 2A or 2B phenotype with no mutation, an acquired von Willebrand syndrome (AVWS) was suspected/confirmed. These data seem to support NGS as a first line efficient and faster paradigm in VWD diagnosis.

Inherited ADAMTS13 deficiency (Upshaw-Schulman syndrome): a short review.

Congenital thrombotic thrombocytopenic purpura (TTP), also known as Upshaw-Schulman syndrome, is associated with an inherited deficiency of ADAMTS13, a von Willebrand factor-cleaving protease. It is a rare, life-threatening disorder characterized by thrombocytopenia, hemolytic anemia, neurological symptoms, renal dysfunction, and fever resulting from formation of platelet thrombi within the microvasculature. Patients have initial episodes mainly during infancy or early childhood, and are conventionally treated with fresh frozen plasma. However, a more appropriate approach based on recombinant ADAMTS13 is slated to begin shortly. Mutations throughout the ADAMTS13 have been identified in congenital TTP patients. The prevalence of this entity is probably underestimated because it is often not suspected, the clinical course is usually heterogeneous and most of the symptoms are common to other diseases. The present review summarizes our current knowledge about Upshaw-Schulman syndrome.

VWF propeptide and ratios between VWF, VWF propeptide, and FVIII in the characterization of type 1 von Willebrand disease.

During posttranslational modifications of von Willebrand factor (VWF), the VWF propeptide (VWFpp) is cleaved. The ratio between VWFpp and VWF antigen (VWF:Ag) and the ratio between factor VIII (FVIII:C) and VWF:Ag may be used to assess synthesis and clearance of VWF. We analyzed the contribution of VWFpp and ratios of VWFpp/VWF:Ag and FVIII:C/VWF:Ag in the pathophysiological characterization of type 1 von Willebrand disease (VWD) in the Molecular and Clinical Markers for the Diagnosis and Management of Type 1 VWD (MCMDM-1VWD) study. The VWFpp/VWF:Ag and FVIII:C/VWF:Ag ratios were increased among patients compared with unaffected family members and healthy controls. The VWFpp/VWF:Ag ratio was higher in individuals heterozygous for missense mutations than in those heterozygous for null alleles. In contrast, the FVIII:C/VWF:Ag ratio was highest among heterozygotes for VWF null alleles. The ratios of VWFpp/VWF:Ag and FVIII:C/VWF:Ag indicate that the pathophysiological mechanisms of type 1 VWD include reduced production and accelerated clearance of VWF, but that often a combination of both mechanisms is implicated.

Emerging viral infections­-a potential threat for blood supply in the 21st century.

During the last 25 years the safety of blood products has improved dramatically with regard to infectious risk, notably to the threat represented by retroviruses (HIV and human T­cell lymphotropic virus) and hepatitis B and C viruses. However, both residual and emergent viral infections are still responsible for contaminations in recipients of blood products. Along with other viruses (human herpesvirus­8, human parvovirus B19, hepatitis A and E viruses, etc.), special attention has recently been paid to emerging arboviruses, such as West Nile virus in North America, and Dengue and Chikungunya viruses in Europe. Another blood­linked risk, notably in the United Kingdom and France, is the prion agent responsible for the variant form of the Creutzfeldt­Jakob disease. Hemophilia care has been the model for improvements in the safety and availability of safe blood components free of infectious agents. In this regard, several measures aimed to halt transmission of viruses have been implemented in blood banks, including the exclusion of at­risk donors, specific sensitive diagnostic tests, leukocyte reduction of labile blood products, and the physical or chemical treatments aiming at nonspecific inactivation of infectious agents potentially present in blood without impairing significantly its physiological properties.

Diagnosis and management of von Willebrand disease in Spain.

The correct diagnosis and classification of Von Willebrand disease (VWD) is important for therapy and genetic counseling but is made difficult due to the variability of its clinical expression and limitations of laboratory methods. A national registry of VWD patients has been initiated in Spain. The results of a concise survey on the diagnosis of VWD show the frequency of VWD is fivefold greater in Spain than that expected from epidemiological studies in other European countries; this may result from overdiagnosis and/or a higher prevalence of VWD. These results clearly reinforce the need for the Spanish VWD registry. A consensus guideline for optimal treatment of VWD is being elaborated in Spain. Desmopressin (DDAVP) is the choice of treatment in responsive VWD patients. Von Willebrand factor concentrates (VWF/factor VIII) are used in individuals nonresponsive to DDAVP, when DDAVP is contraindicated, or in VWD types 2B and 3.

Acquired von Willebrand syndrome and mitral valve prosthesis leakage. A pilot study.

BACKGROUND: Of patients with severe aortic stenosis, 15-25% present with bleeding episodes possibly attributable to acquired von Willebrand syndrome (AVWS). AVWS associated with mitral valve prosthesis leakage has not been reported. METHODS AND RESULTS: Five patients receiving appropriate oral anticoagulation showed mitral valve prosthesis leakage and bleeding episodes; all of them required hospitalization and two blood transfusions, and a von Willebrand factor (VWF) analysis was performed. Two patients with normal functioning metallic prosthesis valves were included as controls. Before surgery, after cessation of acenocumarol, the patients had prolonged activated partial thromboplastin time; four had prolonged closure time (CT) from the platelet function analyzer. Factor VIII procoagulant activity (FVIII:C), VWF ristocetin cofactor activity (VWF:RCo), and VWF collagen binding (VWF:CB) were considerably elevated, while VWF antigen (VWF:Ag) was most elevated. Disproportionate VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios were seen with the loss of large VWF multimers. Following surgery, all parameters were markedly increased and the ratios, CT, and multimeric VWF profile became normal. CONCLUSIONS: Acquired VWF qualitative alterations in mitral valve prosthesis leakage may be associated with or contribute to bleeding diathesis. AVWS should be taken into consideration in patients with mitral valve prosthesis leakage with bleeding diathesis not explained by excessive oral anticoagulation.

The impact of bleeding history, von Willebrand factor and PFA-100(®) on the diagnosis of type 1 von Willebrand disease: results from the European study MCMDM-1VWD.

The relationships between the Platelet Function Analyzer (PFA)-100 and von Willebrand factor (VWF) levels and bleeding score (BS) were evaluated within a multicentre project on Molecular and Clinical Markers for the Diagnosis and Management of type 1 von Willebrand disease (MCMDM-1VWD). PFA-100 closure time, either with epinephrine (EPI) or adenosine diphosphate (ADP)-cartridges, was measured in 107 index cases, 105 affected and 71 unaffected family members, and 79 healthy controls. By regression analysis VWF levels were strongly related to both closure times, with a non-linear progression. In a multiple stepwise regression model, age- and sex-adjusted PFA-100 ADP and VWF ristocetin cofactor activity (VWF:RCo) were independently associated with BS. Most of the variation of BS was predicted by PFA-100 ADP and VWF:RCo alone. In the subgroup of patients with subtle abnormalities of the multimeric pattern, VWF was invariably reduced and closure time prolonged in almost all of them. Neither PFA-100 ADP nor EPI closure times appeared to significantly improve the diagnostic capability of VWF antigen (VWF:Ag) measurement. Thus, in an unselected population a normal PFA-100 would be useful to exclude VWD, but whether it could replace the more specific VWF assay in patients with significant mucocutaneous bleeding symptoms remains to be investigated prospectively.

Von Willebrand factor/factor VIII concentrates in the treatment of von Willebrand disease.

Therapy for von Willebrand disease (VWD) aims to restore the hemostatic function conferred by von Willebrand factor (VWF), which facilitates platelet adhesion and aggregation, and serves to increase potentially low coagulation factor VIII (FVIII) in plasma. In patients unresponsive to desmopressin (DDAVP), the preferred treatment is with plasma-derived VWF-containing FVIII concentrates. Only a few of the available VWF/FVIII concentrates have been licensed for use in VWD based on prospective studies. The efficacy of VWF/FVIII concentrates depends on the content and quality of VWF and FVIII. Several studies have demonstrated the variability of the VWF contents, as well as the differences in the VWF multimer patterns (including the high molecular weight VWF multimers that are most effective in restoring hemostasis), among these concentrates. Treating physicians should be aware of these disparities and the potential clinical implications for patients with different VWD subtypes. Dosing has traditionally been calculated based on the FVIII content of the products, although dosing based on VWF functional activity [e.g., VWF ristocetin cofactor activity (VWF:RCo)] addresses the primary protein deficiency in VWD patients. Several clinical studies have demonstrated the efficacy of concentrates dosed according to VWF:RCo. Dosing is generally consistent across VWD subtypes, although patients with severe phenotypes or undergoing major procedures may require more infusions or longer treatment duration. Other considerations for the use of VWF-containing concentrates include laboratory monitoring of efficacy and safety issues such as thrombosis risk and thromboprophylaxis.

Autosomal dominant von Willebrand disease type 2M.

von Willebrand disease (VWD) type 2M is a distinct entity and clearly differs from type 1. The genotype-phenotype correlation for cases with ristocetin cofactor activity (RCo)/antigen (Ag) ratios <0.60 is clear, whereas the von Willebrand factor (VWF):collagen binding (CB)/VWF:Ag ratio is normal in VWD 2M. Typical laboratory features of VWD type 2 M are decreased ristocetin-induced platelet aggregation in the presence of a normal or near normal VWF multimeric pattern on a low-resolution agarose gel, a poor response to desmopressin (DDAVP) of VWF:RCo, and a good response of both VWF:CB and VWF:Ag to DDAVP. The phenotypic definition of VWD type 2M may need to be more stringent and should be the subject of an international standardization initiative.

Autosomal dominant C1149R von Willebrand disease: phenotypic findings and their implications.

BACKGROUND: Mutation C1149R in the von Willebrand factor (VWF) gene has been thought to cause autosomal dominant severe type 1 von Willebrand disease (VWD). DESIGN AND METHODS: Eight patients from three unrelated families with this mutation were included in the present study who had distinct VWF abnormalities, not described in earlier studies. RESULTS: The patients showed notably low levels of VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), VWF collagen binding (VWF:CB), and a reduced ristocetin-induced platelet aggregation (RIPA). VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios were lower than 0.7. At basal conditions, all the VWF multimers were decreased in plasma, with a clearly lower relative proportion of the high molecular weight VWF multimers (HMWM). In high-resolution agarose gels, a large decrease in the relative proportions of the satellite bands was seen. The patients had a brief good response to desmopressin (DDAVP) administration, but the released VWF half-life was shorter than normal, indicating an accelerated clearance of their VWF. Platelet VWF was abnormal. CONCLUSIONS: We conclude from the results obtained in these patients for plasma phenotypic data that this mutation should be classified as a VWD type 2A (IIE). DDAVP therapy may be somewhat helpful for this mutation, at least for mild to moderate bleeding. These data provide evidence that for VWD classification factors other than basal VWF, such as DDAVP response and platelet VWF, should be considered.

Consensus opinion for the selection and use of therapeutic products for the treatment of haemophilia in Spain.

The period between isolation of HIV in the early 1980s and the development of effective viral inactivation procedures able to eradicate the virus from the blood supply was long and unfortunately many recipients of blood-derived products became infected; this translated into a devastating impact on their quality of life, quality of care as well as on their life expectancy. Some years later, hepatitis C virus infection was identified as another known blood-borne disease complicating the treatment of haemophilia. Nowadays, the potential threat of emerging new pathogens has stressed the need to provide effective but primarily safe products with regard to infectious agents, as well as to regularly update therapeutic guidelines for haemophilia. The aim of the present publication was to review some of the crucial aspects related to the choice of haemostatic concentrates for the treatment of haemophilia and other inherited bleeding disorders, to analyse the current situation in the United States, Canada and European Union countries and to report the most relevant aspects of the Spanish consensus opinion of haemophilia-treating doctors for the use of therapeutic products for haemophilia recently issued. Essentially, it suggests that a gradual switch to recombinant concentrates may be a beneficial decision for patients with haemophilia and for the National Health Service.

Identification of type 1 von Willebrand disease patients with reduced von Willebrand factor survival by assay of the VWF propeptide in the European study: molecular and clinical markers for the diagnosis and management of type 1 VWD (MCMDM-1VWD).

The decreased survival of von Willebrand factor (VWF) in plasma has been implicated as a mechanism in a subset of type 1 von Willebrand disease (VWD) patients. We have previously reported that the ratio of plasma levels of VWF and its propeptide (VWFpp) can be used to identify patients with reduced VWF survival. In this study, we report the assay of VWFpp and VWF:Ag in 19 individuals recruited from 6 European centers within the MCMDM-1VWD study. Eight individuals had a VWF:Ag level less than 30 IU/dL. Seven of these patients had a robust desmopressin response and significantly reduced VWF half-life that was predicted by a markedly increased steady-state plasma VWFpp/VWF:Ag ratio. VWF mutations previously associated with reduced VWF survival were identified in each of the 7 individuals. Thus, a substantially increased ratio of steady-state VWFpp/VWF:Ag predicted a reduced VWF half-life in patients with markedly decreased VWF:Ag levels. These data indicate that a reduced VWF survival is found in a subpopulation of patients with type 1 VWD. The systematic assay of both plasma VWF and the VWF propeptide in moderately severe type 1 VWD patients may identify patients with a reduced VWF survival phenotype.