Genotyping is not routinely performed at diagnosis of von Willebrand disease (VWD). Therefore, the association between genetic variants and pathogenic mechanism or the clinical and laboratory phenotype is unknown in most patients, especially in type 1 VWD. To investigate whether genotyping adds to a better understanding of the pathogenic mechanisms and variability in phenotype, we analyzed the VWF gene in 390 well-defined VWD patients, included in the WiN study. A VWF gene variant was found in 155 patients (61.5%) with type 1, 122 patients (98.4%) with type 2, and 14 patients (100%) with type 3 VWD. Forty-eight variants were novel. For each VWF gene variant, the pathogenic mechanisms associated with reduced VWF levels was investigated using the FVIII:C/VWF:Ag and VWFpp/VWF:Ag ratios. In type 1 VWD, reduced synthesis or secretion of VWF was most frequently found in patients with nonsense variants, frameshift variants, and deletions, whereas rapid clearance of VWF was mainly found in patients with missense variants. Furthermore, type 1 VWD patients with and without a VWF gene variant were clearly distinct in their clinical features such as age of diagnosis, laboratory phenotype, and bleeding phenotype. In type 2 VWD, 81% of variants were associated with an increased clearance of VWF. To conclude, we identified the pathogenic mechanisms associated with various VWF gene variants in type 1, 2, and 3 VWD patients. Additionally, major differences in the phenotype of type 1 VWD patients with and without a variant were observed, which may be of importance for clinical management.

Von Willebrand factor (VWF) multimer analysis is important in the classification of von Willebrand disease (VWD). Current visual VWF multimer analysis is time consuming and inaccurate in detecting subtle changes in multimer patterns. Although VWF multimer densitometric analysis may be useful, the accuracy needs further investigation before it can be widely applied. In this study we aimed to validate VWF multimer densitometric analysis in a large cohort of VWD patients and to identify patient characteristics associated with densitometric outcomes. Patients were included from the Willebrand in the Netherlands (WiN) study, in which a bleeding score (BS) was obtained, and blood was drawn. For multimer analysis, citrated blood was separated on an agarose gel and visualized by Western blotting. IMAGEJ was used to generate densitometric images and medium-large VWF multimer index was calculated. We included 560 VWD patients: 328 type 1, 211 type 2, and 21 type 3 patients. Medium-large VWF multimer index performed excellent in distinguishing visually classified normal VWF multimers from reduced high-molecular-weight (HMW) multimers (area under the curve [AUC]: 0.96 [0.94-0.98], P < 0.001), normal multimers from absence of HMW multimers (AUC 1.00 [1.00-1.00], P < 0.001), and type 2A and 2B from type 2M and 2N (AUC: 0.96 [0.94-0.99], P < 0.001). Additionally, higher medium-large VWF multimer index was associated with lower BS in type 1 VWD: β = -7.6 (-13.0 to -2.1), P = 0.007, adjusted for confounders. Densitometric analysis of VWF multimers had an excellent accuracy compared with visual multimer analysis and may contribute to a better understanding of the clinical features such as the bleeding phenotype of VWD patients.

Background: The bleeding phenotype of von Willebrand disease (VWD) varies highly between patients and can only partly be explained by von Willebrand factor (VWF) parameters. By cleaving large VWF multimers into smaller, less active multimers, ADAMTS-13 is an important regulator of VWF activity. However, it is unknown what the role of ADAMTS-13 is in individuals with VWD. Objectives: We therefore studied how ADAMTS-13 activity is associated with the laboratory and bleeding phenotype in individuals with VWD. Methods: We measured ADAMTS-13 activity using the fluorescence resonance energy transfer substrate VWF 73 assay in 638 individuals with VWD in the nationwide cross-sectional Willebrand in the Netherlands study and in 36 healthy controls. The bleeding phenotype was assessed using the Tosetto bleeding score. Results: ADAMTS-13 activity was similar in individuals with VWD (109% +/- 20.6%) and controls (110% +/- 19.7%). ADAMTS-13 activity was higher in individuals with VWD with type 3 than those with type 1 (mean difference, 11.8%; 95% confidence interval [CI], 2.9%-20.8%) or type 2 (mean difference, 16.1%; 95% CI, 7.1%-25.1%). ADAMTS-13 activity was not associated with the Tosetto bleeding score (0.1 Tosetto bleeding score increase per 10% ADAMTS-13 increase, 95% CI, -0.2 to 0.3). Furthermore, ADAMTS-13 activity did not differ between individuals with and without a bleeding event during the year preceding blood sampling (mean difference, 1.4%; 95% CI, -2.1% to 4.9%). Conclusion: ADAMTS-13 activity was highest in individuals with type 3 VWD, but it had only minor associations with VWF parameters. ADAMTS-13 activity does not influence the bleeding phenotype in individuals with VWD.

The bleeding phenotype of patients with type 1 von Willebrand disease (VWD) is very heterogeneous. We hypothesized that this heterogeneity may partly be explained by variability in response of von Willebrand factor (VWF) and factor VIII (FVIII) levels to stress during hemostatic challenges. We therefore investigated whether VWF and FVIII levels after administration of desmopressin, which mimic in vivo hemostatic response during hemostatic challenges, explain the heterogeneity in bleeding phenotype of patients with type 1 VWD. We performed a retrospective cohort study in 122 patients with type 1 VWD. All patients received a test dose of desmopressin shortly after diagnosis. Patients' mean age was 47 ± 14 years, and the mean Tosetto bleeding score was 10 ± 7. Higher FVIII activity during the complete time course after desmopressin administration (1, 3, and 5-6 hours), and higher VWF and FVIII levels combined at 3 hours after desmopressin administration, were associated with a lower bleeding score: β = -0.9 (-1.7; -0.1) and β = -1.2 (-1.9; -0.5), respectively, adjusted for age, sex, body mass index (BMI), and comorbidities. Patients with FVIII activity in the highest quartile 3 hours after desmopressin administration had a much lower bleeding score compared with patients in the other 3 quartiles (β = -5.1 [-8.2; -2.0]) and also had a lower chance of an abnormal bleeding score (odds ratio = 0.2 [0.1-0.5]), both adjusted for age, sex, BMI, and comorbidities. In conclusion, VWF and FVIII levels after desmopressin administration, which mimic hemostatic response to hemostatic challenges, are associated with the bleeding phenotype of patients with type 1 VWD. This may partly explain the variability in bleeding phenotype of these patients.

Low ADAMTS13 activity is associated with an increased risk of cardiovascular disease, which is generally attributed to its proteolytic effects on Von Willebrand factor (VWF). Cardiovascular health is an important determinant of cognitive decline, but the association of either VWF or ADAMTS13 with risk of dementia is unknown. Between 1997–2002, we measured VWF antigen and ADAMTS13 activity in 6055 participants of the population-based Rotterdam Study (mean age 69.3 years, 57.2% women). At baseline, 85 participants had dementia, and during 15 years of follow-up 821 developed dementia. Higher VWF was associated with prevalence and risk of dementia, unaffected by concurrent ADAMTS13 activity, but estimates strongly attenuated over time and were no longer statistically significant at 4 years of follow-up (relative risks [95% CI] per standard deviation increase– cross-sectional: 1.37 [1.06–1.77], and longitudinal: 1.05 [0.97–1.14]). In contrast, low ADAMTS13 was associated with increased risk of dementia throughout follow-up (hazard ratio per SD decrease– 1.16 [1.06–1.28]), which alike for ischaemic stroke, was modified by the presence of diabetes (P-interaction = 0.003). In conclusion, higher VWF and low ADAMTS13 activity are associated with increased risk of dementia, but differences in time-course and lack of synergistic effects may indicate in part independent underlying mechanisms.

IntroductionPatients with Von Willebrand disease (VWD) are regularly treated with VWF-containing concentrates in case of acute bleeding, trauma and dental or surgical procedures. AimIn this multicentre retrospective study, current perioperative management with a von Willebrand factor (VWF)/Factor VIII (FVIII) concentrate (Haemate((R)) P) in patients with VWD was evaluated. Patients/MethodsPatients with VWD undergoing minor or major surgery between 2000 and 2015, requiring treatment with a VWF/FVIII concentrate (Haemate((R)) P), were included. Achieved VWF activity (VWF:Act) and FVIII during FVIII-based treatment regimens were compared to predefined target levels in national guidelines. ResultsIn total, 103 patients with VWD (148 surgeries) were included: 54 type 1 (73 surgeries), 43 type 2 (67 surgeries) and 6 type 3 (8 surgeries). Overall, treatment resulted in high VWF:Act and FVIII levels, defined as 0.20IU/mL above predefined levels. In patients with type 1 VWD, respectively, 65% and 91% of trough VWF:Act and FVIII levels were higher than target levels. In patients with type 2 and type 3 VWD, respectively, 53% and 57% of trough VWF:Act and 72% and 73% of trough FVIII levels were higher than target level. Furthermore, FVIII accumulation over time was observed, while VWF:Act showed a declining trend, leading to significantly higher levels of FVIII than VWF:Act. ConclusionHigh VWF:Act and accumulation of FVIII were observed after perioperative FVIII-based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.

Background Measuring the ability of von Willebrand factor (VWF) to bind to platelets is crucial for the diagnosis and classification of von Willebrand disease (VWD). Several assays that measure this VWF activity using different principles are available, but the clinical relevance of different assay principles is unclear. Objective To compare the four most widely used VWF activity assays in a large VWD patient population. Methods We measured VWF:RCo (ristocetin to activate VWF + whole platelets), VWF:GPIbR (ristocetin + platelet glycoprotein Ib receptor [GPIb] fragments), VWF:GPIbM (gain-of-function GPIb fragments that bind VWF spontaneously without ristocetin) and VWF:Ab (monoclonal antibody directed against the GPIb binding epitope of VWF to mimic platelets) in 661 VWD patients from the nationwide 'Willebrand in the Netherlands' (WiN) Study. Results All assays correlated excellently (Pearson r > 0.9), but discrepant results led to a different classification for up to one-fifth of VWD patients. VWF:RCo was not sensitive enough to classify 18% of patients and misclassified half of genotypic 2B VWD patients, especially those with p.Arg1306Trp. VWF:GPIbR was more sensitive, accurately classified the vast majority of patients, and was unaffected by the p.Asp1472His variant that causes artificially low VWF:RCo. VWF:GPIbM was the most precise assay but misclassified over a quarter of genotypic 2A, 2B and 3 patients. VWF:Ab, often not considered an actual VWF activity assay, performed at least equally to the other assays with regard to accurate VWD classification. Conclusion Although the different VWF activity assays are often considered similar, differences between assays have a large impact on the classification of VWD.

In this issue of Blood, Lavin et al report their study of 126 patients who presented at the Irish Reference Center for Bleeding Disorders with bleeding symptoms and von Willebrand factor (VWF) levels between 30 and 50 IU/dL, often referred to as “low VWF.”1

Introductionvon Willebrand disease (VWD) is the most common inherited bleeding disorder. In VWD patients, large variations in bleeding tendency are observed, which cannot be completely explained by the variation in von Willebrand factor levels or activities. Thus, there must be additional factors, for instance, changes in fibrinolysis that have an effect on the variation in bleeding tendency in VWD patients.AimTo investigate whether plasminogen activator inhibitor‐1 (PAI‐1) level influences the variation in bleeding tendency in VWD patients.MethodsPAI‐1 antigen levels were measured in the plasma of 633 patients with moderate or severe VWD who participated in the ‘Willebrand in the Netherlands’ (WiN) study, a nationwide multicentre cross‐sectional study. Bleeding severity was assessed using the Tosetto bleeding score.ResultsPAI‐1 levels increased with age (Spearman's rho: 0.225, P < 0.001) and were higher in men (23 [IQR 12–60] vs. 20 [IQR 10–44] ng mL−1 in women, P = 0.039), whereas the bleeding score was higher in women (11 [IQR 7–17] vs. 9 [IQR 5–14] ng mL−1 in men, P = 0.002). After adjustment for age and sex by stratification, PAI‐1 level and bleeding score were negatively correlated (Spearman's rho: −0.170, P = 0.017) in the group of 196 young (age ≤ 45 year) female VWD patients, accounting for 31% of our study population.ConclusionIn young female VWD patients, we observed that low PAI‐1 levels were associated with a higher bleeding score, which may partly explain the observed variability in bleeding phenotype in VWD patients.

Mild inherited bleeding disorders are relatively common in the general population. Despite recent advances in diagnostic approaches, mild inherited bleeding disorders still pose a significant diagnostic challenge. Hemorrhagic diathesis can be caused by disorders in primary hemostasis (von Willebrand disease, inherited platelet function disorders), secondary hemostasis (hemophilia A and B, other (rare) coagulant factor deficiencies) and fibrinolysis, and in connective tissue or vascular formation. This review summarizes the currently available diagnostic methods for mild bleeding disorders and their pitfalls, from structured patient history to highly specialized laboratory diagnosis. A comprehensive framework for a diagnostic approach to mild inherited bleeding disorders is proposed.

Von Willebrand factor (VWF) levels vary over time and increase throughout life in both healthy individuals and patients with von Willebrand disease (VWD). Especially in type 1 VWD patients, this increase may result in normalization of VWF levels. It is not yet known if normalization of VWF levels ameliorates bleeding symptoms in VWD patients. We have recently shown that elderly type 1 VWD patients had similar bleeding tendency as younger adults.1 However, many elderly patients in this study had relatively low VWF levels and many younger adults had relatively high VWF levels.1 The aim of the current study was to investigate the association between normalization of VWF levels and the bleeding phenotype in type 1 VWD patients.

Von Willebrand factor (VWF) has an important role in haemostasis by mediating platelet adhesion and aggregation. Higher activity of VWF is associated with increased risk of myocardial infarction and ischaemic stroke, but its impact on the risk of developing dementia is unknown. We determined levels of VWF in participants of the ongoing population-based Rotterdam Study. We determined the risk of dementia and Alzheimer’s disease in relation to VWF, using a Cox model adjusted for age, sex, renal function, cardiovascular risk factors, use of antiplatelet drugs, and apolipoprotein E genotype. We repeated analyses after excluding and censoring for stroke, excluding those with a history of vascular disease, and stratifying for blood type O vs. A/B/AB. We furthermore determined decline in test scores on a cognitive assessment battery in relation to baseline levels of VWF, using linear regression. Of 6366 initially non-demented participants (mean±SD age 69.1±8.1, 56.5% women) with a mean follow-up of 9.2 years, 590 developed dementia, of whom 480 (81.1%) Alzheimer’s disease. Higher baseline levels of VWF were associated with an increased risk of dementia (adjusted HR, 95% CI, per SD increase 1.09, 1.00-1.19; p=0.04), and Alzheimer’s disease (aHR 1.14, 1.03-1.25; p=0.01). These results were unaffected by taking into account stroke or excluding participants with a history of vascular disease, and similar across blood types. During repeated cognitive assessment in non-demented participants after on average 4.4 years of follow-up, higher baseline levels of VWF were associated with accelerated decline in global cognition (p=0.002). Higher levels of Von Willebrand factor are associated with an increased risk of dementia, including Alzheimer’s disease, possibly due to direct prothrombotic effects or secondary to endothelial injury.

BACKGROUNDAltered levels of von Willebrand factor (vWF) and ADAMTS13 can promote thrombosis and disturb blood flow in kidney microcirculations. We investigated the association of serum vWF:ADAMTS13 ratio in relation to decline in kidney function.STUDY DESIGNProspective cohort study.SETTING & PARTICIPANTS2,479 individuals (mean age, 65.1±5.9 [SD] years; 43% men) from the population-based Rotterdam Study.PREDICTORSvWF, ADAMTS13, and vWF:ADAMTS13 ratio.OUTCOMES & MEASUREMENTSAnnual decline in estimated glomerular filtration rate (eGFR), halving of eGFR, and new-onset eGFR<60mL/min/1.73m2 were assessed.RESULTSDuring a median follow-up of 11 (range, 7.81-13.57) years, 500 cases of new-onset eGFR<60mL/min/1.73m2 occurred. The population had a mean eGFR decline of 0.96±0.92mL/min/1.73m2 per year. Higher vWF:ADAMTS13 ratio was associated with steeper annual decline in eGFR (difference, -0.06 [95% CI, -0.09 to -0.02] mL/min/1.73m2 per year) and higher risk for new-onset eGFR<60mL/min/1.73m2 (OR, 1.13; 95% CI, 1.01-1.27). Likewise, higher vWF:ADAMTS13 ratio was associated with higher risk for halving of eGFR (OR, 1.40; 95% CI, 1.02-1.93). After adjustment for cardiovascular risk factors and blood group, effect estimates remained the same.LIMITATIONSNo data available for albuminuria. Participants were classified based on a single measurement of vWF and ADAMTS13.CONCLUSIONSIn this population-based study, we showed that higher vWF:ADAMTS13 ratio is associated with decline in kidney function, suggesting a role of elevated prothrombotic factors in the development and progression of kidney disease.

a Maastricht University, Cardiovascular Research Institute Maastricht (CARIM), Department of Biochemistry, Maastricht, The Netherlands b University of Yamanashi, Department of Clinical and Laboratory Medicine, Yamanashi, Japan c The Scripps Research Institute, Department of Immunology and Microbial Science, La Jolla, CA, USA d University Medical Center Mainz, Center for Thrombosis and Hemostasis, Mainz, Germany e Synapse BV and Cardiovascular Research Institute Maastricht (CARIM), Maastricht, The Netherlands f University of Aberdeen, Institute of Medical Sciences, Aberdeen, UK g University of Pennsylvania, Institute for Medicine and Engineering, Philadelphia, PA, USA h Academic Medical Centre of the University of Amsterdam, Department of Clinical Chemistry, Amsterdam, The Netherlands i Leiden University Medical Centre, Department of Thrombosis and Hemostasis, Einthoven Laboratory for Experimental Vascular Medicine, Leiden, The Netherlands j Erasmus University Medical Center, Department of Hematology, Rotterdam, The Netherlands