Low Von Willebrand Factor Levels Research Articles

Common and Rare Variants in Genes Associated with von Willebrand Factor Level Variation: No Accumulation of Rare Variants in Swedish von Willebrand Disease Patients.

Genome-wide association studies (GWASs) have identified genes that affect plasma von Willebrand factor (VWF) levels. ABO showed a strong effect, whereas smaller effects were seen for VWF , STXBP5 , STAB2 , SCARA5 , STX2 , TC2N , and CLEC4M . This study screened comprehensively for both common and rare variants in these eight genes by resequencing their coding sequences in 104 Swedish von Willebrand disease (VWD) patients. The common variants previously associated with the VWF level were all accumulated in the VWD patients compared to three control populations. The strongest effect was detected for blood group O coded for by the ABO gene (71 vs. 38% of genotypes). The other seven VWF level associated alleles were enriched in the VWD population compared to control populations, but the differences were small and not significant. The sequencing detected a total of 146 variants in the eight genes. Excluding 70 variants in VWF , 76 variants remained. Of the 76 variants, 54 had allele frequencies > 0.5% and have therefore been investigated for their association with the VWF level in previous GWAS. The remaining 22 variants with frequencies < 0.5% are less likely to have been evaluated previously. PolyPhen2 classified 3 out of the 22 variants as probably or possibly damaging (two in STAB2 and one in STX2 ); the others were either synonymous or benign. No accumulation of low frequency (0.05–0.5%) or rare variants (<0.05%) in the VWD population compared to the gnomAD (Genome Aggregation Database) population was detected. Thus, rare variants in these genes do not contribute to the low VWF levels observed in VWD patients.

Blood Markers of Portal Hypertension Are Associated with Blood Loss and Transfusion Requirements during Orthotopic Liver Transplantation.

There is increasing evidence that portal hypertension plays a major role in bleeding risk during orthotopic liver transplantation (OLT). We investigated the association between preoperative blood levels of von Willebrand factor (VWF) and soluble CD163 (sCD163), which are established markers of portal hypertension, and blood loss and transfusion requirements during OLT. We measured levels of VWF and sCD163 in preoperative serum samples of 168 adult patients undergoing a primary OLT between 1998 and 2012. Preoperative levels of VWF and sCD163 correlated with the model of end-stage liver disease (MELD) score (r = 0.414, p < 0.001 and r = 0.382, p < 0.001, respectively). Patients with high VWF or sCD163 levels (VWF and sCD163 levels above the median) had a substantially increased risk of needing red blood cell transfusion compared with patients with low VWF or sCD163 levels (VWF and sCD163 levels below the median) (odds ratio 3.5 [95% confidence interval, CI 1.7-7.0] and 2.3 [95% CI 1.1-4.5], respectively). Blood loss was highest in patients with both high VWF or sCD163 levels and a high preoperative international normalized ratio. Elevated blood levels of markers of portal hypertension are associated with increased blood loss and transfusion requirements during OLT and support the notion that portal hypertension is an important contributor to perioperative blood loss.

Von Willebrand factor, ABO blood group, and risk of first-ever intracerebral hemorrhage: A prospective nested case-control study

Background and purposeLow levels of von Willebrand factor (VWF) were associated with intracerebral hemorrhage (ICH) in a previous study. Persons with blood group O have lower VWF levels than other ABO blood groups. This study aimed to investigate the association between VWF and the risk of ICH in adults, as well as the association between ABO blood group and risk of ICH. MethodsThis population-based, nested case-control study was conducted using data and blood samples from health examinations between 1985 and 2007. All participants were followed, and cases with first-ever ICH were identified and validated. One or two controls were matched to each case. ResultsDuring a median follow-up time from blood sampling to ICH of 5.6 years, 176 cases with ICH were identified. The mean age at health examination was 57 years; 50% of participants were women. There was an association between hypertension and risk of ICH, but there was no association between VWF level and risk of ICH. There was no association between blood group O and risk of ICH. ConclusionsTo our knowledge this is the largest prospective study investigating the association between VWF, ABO blood group and ICH. We found no association between VWF or blood group O and risk of future ICH.

Low VWF levels in children and lack of association with bleeding in children undergoing tonsillectomy

Abstractvon Willebrand disease is a common bleeding disorder, but diagnosis can be difficult in young children who have not had bleeding challenges. We sought to evaluate the correlation between bleeding and von Willebrand factor (VWF) levels in children undergoing surgical challenge with tonsillectomy. Children ages 0 to 18 undergoing tonsillectomy without a personal or family history of bleeding were enrolled prospectively following informed consent and institutional review board approval. VWF levels were obtained at the time of surgery. VWF antigen (VWF:Ag) and VWF activity (VWF:GPIbM) were tested via enzyme-linked immunosorbent assay. Bleeding score was calculated using the International Society of Hematology bleeding assessment tool (BAT). Surgical and postoperative bleeding were determined using questionnaires filled out by the surgeon and patient/family. A total of 1399 subjects were enrolled with evaluable data, with a median age of 5 years. The median VWF:Ag was 85 IU/dL and the median VWF:GPIbM was 100 U/dL. Median BAT for the entire population was 0, including those with postoperative bleeding. There was no difference in VWF level between those who experienced postoperative bleeding and those who did not, with median VWF:Ag 85 vs 85 (P = .89) and mean VWF:GPIbM 98 vs 100 (P = .5). Interestingly, there was a difference in VWF levels with age, with median VWF:Ag 81 for those younger than 3 years, 82 for those 3 to 6 years, 90 for those 7 to 10 years, and 100 for those 11 to 18 years. A similar trend was noted for VWF:GPIbM. Of the 2 to 6 year olds, 5% had VWF:Ag <50, which would meet criteria for low VWF, but only 1.8% had an abnormal BAT at study entry and only 2.5% bled after surgery. Only 1 subject with low VWF had an elevated postoperative BAT >2. These data suggest that low VWF levels do not correlate with bleeding in children undergoing tonsillectomy. In addition, VWF levels outside the adult normal range in young children may be more common than previously thought and do not necessarily predict surgical bleeding.

Perioperative Bleeding Risk Assessment in a Cohort of Children with Low Levels of Von Willebrand Factor

Background: Identifying perioperative bleeding risk in pediatric patients undergoing major surgery is challenging because personal history is often not sufficiently informative and laboratory tests are also more susceptible to pre-analytical variables. Children with low Willebrand add further uncertainty in the treatment options. The aim of this study was to evaluate practices to assess hemorrhagic risk and manage bleeding prophylaxis in children with low von Willebrand factor levels (30 and 50 IU/dL; low VWF), known von Willebrand disease (VWD) or healthy controls undergoing ear, nose and throat (ENT) surgery. Methods: In this retrospective observational study, data from consecutive paediatric patients undergoing ENT surgery between January 1, 2010 and December 31, 2017 at the Turin Paediatric Hospital were analysed. All statistical analyses were performed using STATA (StataCorp. 2013. Been Statistical Software: Release 13. College Station, TX: StataCorp LP). Demographic and clinical characteristics of patients were assessed using the absolute frequencies and percentages for qualitative variables and percentiles for quantitative variables. The risk of bleeding was estimated from the number of patients who experienced bleeding within 21 days as a proportion of the number of patients subjected to surgery. 90% confidence intervals (90% CIs) were estimated for the evaluation of bleeding risk, using the Jeffreys method and any differences in the risk of bleeding between patient groups were tested using a proportions test. To investigate any factors associated with the therapeutic strategy used, multinomial logistic regression models were conducted. Results: Major perioperative bleeding was seen in 6.3% (5/79) of low VWF patients, 3.0% (35/1152) of healthy controls and 20.0% (5/25) of patients with VWD. In low VWF patients, perioperative bleeding prophylaxis was given to 59.5% and included subcutaneously desmopressin (n=21) and VWF-containing concentrate (n=26). Oral or intravenous tranexamic acid was administered to all low VWF patients. Of these patients, one major hemorrhagic event occurred in patients who did not receive prophylaxis and the remaining events occurred in patients treated with VWF-containing concentrate. In patients who received a VWF-containing concentrate, lower VWF ristocetin cofactor levels were observed compared with patients who received desmopressin or were untreated during surgery. No differences in clinical and laboratory features were observed between patients with low VWF treated with desmopressin and those who were untreated. Conclusions: Patients with low VWF have a higher risk of perioperative bleeding compared with healthy controls but a significantly lower risk compared with patients with VWD. The perioperative management of these patients is complex with a high risk of overtreatment. In our experience the caution of keeping the VWF-containing concentrate in the operating room available for use in case of bleeding appears to be a balanced approach. Prospective randomized studies to identify accurate methods of assessing bleeding risk and evaluate the most effective perioperative bleeding prevention are warranted. Essential bibliography: Ruchika Sharma and Veronica H. Flood. Advances in the diagnosis and treatment of Von Willebrand disease. Hematology American Society of Hematology Education Program 2017:379-384 Sadler JE. Low von Willebrand factor: sometimes a risk factor and sometimes a disease. Hematology American Society of Hematology Education Program 2009:106-112 Rodeghiero F, Tosetto A, Abshire T, et al. ISTH/SSC bleeding assessment tool: a standardized questionnaire and a proposal for a new bleeding score for inherited bleeding disorders. J Thromb Haemost. 2010;8(9):2063-2065. Casey LJ, Tuttle A, Grabell J, et al. Generation and optimization of the self-administered pediatric bleeding questionnaire and its validation as a screening tool for von Willebrand disease. Pediatr Blood Cancer. 2017;64(10) Mannuccio Mannucci P, Kyrle PA, Schulman S, Di Paola J, Schneppenheim R, Cox Gill J. Prophylactic efficacy and pharmacokinetically guided dosing of a von Willebrand factor/factor VIII concentrate in adults and children with von Willebrand's disease undergoing elective surgery: a pooled and comparative analysis of data from USA and European Union clinical trials. Blood Transfus. 2013;11(4):533-540 Disclosures No relevant conflicts of interest to declare.

VWF and FVIII Levels after Desmopressin Are Associated with the Bleeding Phenotype in Type 1 VWD

Introduction The bleeding phenotype of type 1 von Willebrand disease (VWD) patients is very heterogeneous. We hypothesized that part of this heterogeneity is explained by variability in response of von Willebrand factor (VWF) and factor VIII (FVIII) levels to stress during hemostatic challenges. Patients who have a strong increase in VWF and FVIII levels during hemostatic challenges, may have less frequent or less severe bleeding episodes compared to patients who have a smaller increase in VWF and FVIII levels. Therefore, we investigated whether VWF and FVIII levels after desmopressin, which mimic in vivo hemostatic response during hemostatic challenges, are associated with the bleeding score, and therefore may explain part of the heterogeneity in bleeding phenotype of type 1 VWD patients. Methods In this retrospective cohort study, we included type 1 VWD patients of all ages who were diagnosed and treated in the Erasmus University Medical Center. All patients had a hemorrhagic diathesis or family history of VWD and historically lowest VWF antigen (VWF:Ag) and/or VWF Ristocetin Cofactor activity (VWF:RCo) ≤ 0.30 IU/mL with VWF activity/ VWF antigen ratio above 0.60. All patients participated in the Willebrand in the Netherlands (WiN) study, in which a self-administered Tosetto bleeding score was assessed. Results We identified 173 eligible type 1 VWD patients in our treatment center who participated in the WiN study. After exclusion of 50 patients who did not receive a desmopressin test dose, and 1 patient who did not have a bleeding score assessment, we included 122 type 1 VWD patients. Table 1 shows the patient characteristics. Higher FVIII activity during the complete time course (i.e. one, three and 5-6 hours) after desmopressin, and higher VWF and FVIII levels combined at three hours after desmopressin, were associated with a lower bleeding score, respectively β=-0.9 (95% CI: -1.7; -0.1) and β=-1.2 (-1.9; -0.5), both adjusted for age, sex, BMI and comorbidities. FVIII:C at three hours after desmopressin was significantly associated with a lower bleeding score: β=-1.5 (-3.0; -0.1), whereas VWF levels were not associated (Figure 1). Moreover, patients with VWF and FVIII levels in the highest quartile three hours after desmopressin administration had a lower bleeding score compared to other patients (Figure 2). The largest difference was found for FVIII:C: β=-5.1 (-8.4; -1.8), adjusted for age, sex, BMI, comorbidities and baseline FVIII:C. These patients also less often had an abnormal bleeding score: OR=0.1 (0.0-0.5), adjusted for age, sex, BMI, comorbidities and baseline FVIII:C. Lastly, patients with an increased clearance of VWF, defined as VWF propeptide/VWF:Ag ratio &gt;2.2, had lower VWF:Ag (β=-0.3, -0.6; -0.1), VWF:Act (β=-0.5, -0.7; -0.2), VWF:CB (β=-0.5, -1.0; -0.1) and FVIII:C (β=-0.7, -1.0; -0.4) at three hours after desmopressin administration compared to other type 1 VWD patients, all adjusted for age, sex, BMI and comorbidities. An increased clearance of VWF was also associated with a higher bleeding score: β=3.2 (0.2; 6.2), adjusted for age, sex, BMI, comorbidities and baseline VWF and FVIII levels. Discussion In type 1 VWD patients, the desmopressin induced increase of VWF and FVIII levels is associated with a lower bleeding score. Especially higher VWF and FVIII levels at three hours after desmopressin were associated with a milder bleeding phenotype, suggesting that sustained VWF and FVIII levels after a hemostatic challenge may be important to prevent bleeding. This was strengthened by an association between increased clearance of VWF and a higher bleeding score. Furthermore, patients with VWF and FVIII levels in the highest quartile three hours after desmopressin had 5 points lower bleeding score, and patients with FVIII:C in the highest quartile had 10 times less often an abnormal bleeding score. These results indicate that a good hemostatic response may have important and clinically relevant consequences on the bleeding phenotype, and may compensate for the low baseline VWF and FVIII levels in type 1 VWD patients. In conclusion, VWF and FVIII levels after desmopressin administration, which mimic in vivo hemostatic response to hemostatic challenges, are associated with the bleeding phenotype in type 1 VWD patients. This may partly explain the well-known variability in bleeding phenotype of type 1 VWD patients. Disclosures Atiq: Sobi: Other: Travel grant (ISTH 2019); Professor Heimburger Award 2018 (CSL Behring): Research Funding. Schütte:CSL Behring: Other: Travel grant. Boender:Sobi: Employment; Professor Heimburger Award 2016 (CSL Behring): Research Funding. Kruip:Bayer: Research Funding; Pfizer: Research Funding; Daiichy Sankyo: Research Funding; Boehringer Ingelheim: Research Funding. Leebeek:Shire/Takeda: Consultancy; UniQure: Consultancy; Novo Nordisk: Consultancy; Shire/Takeda: Research Funding; Sobi: Other: Travel grant; CSL Behring: Research Funding.

Bleeding disorders in adolescents with heavy menstrual bleeding in a multicenter prospective US cohort.

Heavy menstrual bleeding is common in adolescents. The frequency and predictors of bleeding disorders in adolescents, especially with anovulatory bleeding, are unknown. Adolescents referred for heavy menstrual bleeding underwent an evaluation of menstrual bleeding patterns, and bleeding disorders determined a priori. The primary outcome was the diagnosis of a bleeding disorder. Two groups were compared: anovulatory and ovulatory bleeding. Multivariable logistic regression analysis of baseline characteristics and predictors was performed. Kaplan Meier curves were constructed for the time from the first bleed to bleeding disorder diagnosis. In 200 adolescents, a bleeding disorder was diagnosed in 33% (n=67): low von Willebrand factor levels in 16%, von Willebrand disease in 11%, and qualitative platelet dysfunction in 4.5%. The prevalence of bleeding disorder was similar between ovulatory and anovulatory groups (31% vs. 36%; P=0.45). Predictors of bleeding disorder included: younger age at first bleed (OR: 0.83; 95%CI: 0.73, 0.96), Hispanic ethnicity (OR: 2.48; 95%CI: 1.13, 5.05), non-presentation to emergency department for heavy bleeding (OR: 0.14; 95%CI: 0.05, 0.38), and International Society on Thrombosis and Haemostasis (ISTH) Bleeding Assessment Tool score ≥4 (OR: 8.27; 95%CI: 2.60, 26.44). Time from onset of the first bleed to diagnosis was two years in the anovulatory, and six years in the ovulatory cohort (log-rank test, P<0.001). There is a high prevalence of bleeding disorders in adolescents with heavy periods, irrespective of the bleeding pattern. Among bleeding disorders, the prevalence of qualitative platelet dysfunction is lower than previously reported.

P13. Abstract Title: Deep Mutational Scan of VWF to Define Mutations that Enhance or Impair Secretion

<h3>Rationale</h3> Von Willebrand Factor (VWF) is a multimeric glycoprotein that recruits platelets to sites of blood vessel injury and serves as a molecular chaperone for coagulation factor VIII (fVIII). Plasma VWF levels are a known risk factor for various thrombotic disorders including VTE, myocardial infarction, and stroke. GWAS studies have identified genetic variants in VWF that contribute to increased and decreased circulating VWF antigen levels. However, it is currently not known why some variants result in high VWF levels while others cause low VWF levels in circulation. We hypothesize that a subset of VWF variants impact its biosynthesis and secretion. <h3>Objective</h3> To identify every possible mutation in VWF that either increase or decrease its biosynthesis and secretion from cells. <h3>Results</h3> We have developed a protein secretion assay in HEK293T-Rex cells based on VWF- eGFP. Mutations in VWF that affect biosynthesis and secretion can be identified based on cell fluorescence intensity using Fluorescence Activated Cell Sorting (FACS). Initial studies have confirmed that cells expressing VWF mutants with known secretion defects have increased intracellular eGFP intensity (eGFP MFI: V1822G=157.72±5.40, C2693Y=184.06±2.10), relative to cells expressing WT VWF (eGFP MFI: WT=69.22±1.87) (p<0.001). This validates that eGFP specific cell retention is a consequence of impaired VWF basal secretion. Mutations of VWF may additionally cause inappropriate VWF secretion in response to physiological stimuli, and exacerbate imbalanced VWF plasma levels under various environmental influences. Cells treated with stimulus show time-dependent stimulation of VWF secretion in cells expressing WT (83.7% MFI reduction, p<0.01) and the C2693Y VWF (46.7% MFI reduction, p<0.01), but minimal response in V1822G VWF expressing cells (8.85% MFI reduction, p<0.05). This suggests that VWF variants may exhibit sensitized/reduced responses to stimulated VWF secretion. <h3>Conclusions</h3> These data provide the proof-of-concept to perform an unbiased deep mutational scan of VWF, to identify every possible mutation that can increase/decrease biosynthesis and secretion. Results of this project will provide a detailed structure/function analysis of VWF in mammalian cells and identify variants in VWF that can impair or enhance its secretion.

Genetics 101: understanding transmission and genetic testing of inherited bleeding disorders

Abstract Haemophilia is an X-linked inherited disorder that affects males and females, though the bleeding risk in girls and women has traditionally been under-recognised. About one third of haemophilia cases occur in individuals where there is no known family history. The gene mutations for rare bleeding disorders are not carried on the X chromosome and are therefore not sex-linked; however, the risk of passing on the condition is greatly increased for consanguineous parents where both parents may carry a copy of the fault in the genetic code which causes the condition. Genetic testing should be offered to every prospective mother, ideally before conception. This should be supported by counselling as the implications for family planning are profound. Von Willebrand factor (VWF) has an important role in primary and secondary haemostasis. Loss of function or low levels of VWF are associated with spontaneous bleeding causing nosebleeds, heavy periods and bruising as well as jpost-surgical bleeding. Joint bleeding and intracranial haemorrhage can also occur in those with a severe type of VWF. Diagnosis depends on bleeding assessment, family history and measurement of VWF. There are three types of VWD: Types 1 and 3 are caused by low or absent levels of VWD; Type 2 is caused by loss of function. Of these, Type 3 VWD is associated with the most severe bleeding risk but there is wide variation in bleeding phenotype among the other sub-types. The correlation between genetic mutation and bleeding phenotype is weak in VWD; therefore genetic testing is mainly useful for interpreting the risk when planning a family and to allow prenatal diagnosis in severe bleeding disorders. Genetic testing is essential for prospective parents to make fully informed decisions about having a family and how or whether to proceed with a pregnancy. The rationale for prenatal testing is to determine the bleeding status of the foetus and to inform decisions about managing delivery. Women may choose to terminate a pregnancy to avoid having a child with severe haemophilia. For some couples the option of adoption or not having children may be explored. Options for prenatal diagnostic testing include non-invasive methods, e.g. assessment of free foetal DNA in maternal plasma to determine the sex of a baby from 10 weeks in pregnancy, and invasive methods, e.g. chorionic villus sampling or amniocentesis, to determine the inheritance of the genetic mutation. Invasive methods are associated with a very small increased risk of pregnancy loss or early labour, which many couples feel is an unacceptable risk. Advanced techniques such as preimplantation screening also available, but require a huge commitment as this involves an IVF technique.

Epigenetic Profiles of Primary Endothelial Cells from Patients with Low VWF Levels

BackgroundVon Willebrand disease (VWD) type 1 is characterized by low von Willebrand factor (VWF) levels and mucocutaneous bleeding (MCB). Approximately 50% of patients with VWD type 1 exhibit mutations in VWF. However, a large number of patients with VWF levels between 30-50 IU/dL do not show mutations in VWF indicating that other mechanisms are involved. Blood outgrowth endothelial cells (BOECs) are a source of donor-specific endothelial cells and have demonstrated impairments in VWF release and packaging in patients with VWD. BOECs have not been evaluated in individuals with low VWF levels.Hypothesis/ObjectiveWe hypothesize that BOECs from individuals with low VWF levels will reveal unique VWF and genome wide epigenetic signatures that may explain the altered plasma VWF levels seen in these patients.MethodsBOEC Derivation: Patients with low VWF levels and MCB (30-50 IU/dL) were enrolled in an IRB-approved study. The mononuclear layer from whole blood was isolated and plated onto collagen coated plates. After extended incubation, the presence of BOECs was confirmed by visual morphology and flow cytometry.VWF Transcriptional Analysis: 9 cells lines including: a) 2 BOEC cell lines from control individuals and a HUVEC cell line and c) BOECs from individuals with low VWF, were assayed via single cell RNA sequencing. Bioinformatic analysis included generalized transcriptional expression and single cell expression of VWF. RNA-sequencing expression data was filtered according to the following standardized algorithm. Cells that were defined as monocytes (TYROBP expression > 2 copies) were excluded. Following monocyte exclusions, cells were determined to be of endothelial origin if they demonstrated the presence of PECAM1, CDH5, ROBO4, ESAM, TIE1, or NOTCH4 transcripts, as previously reported by Butler et al. (Cell Reports, 2016).Epigenetic Profiling:Genomic DNA was extracted from BOECs and from peripheral leukocytes (paired to the BOEC draw sample) and analyzed for DNA methylation via an Illumina 850K methylation array.ResultsBOEC Derivation:A total of eight BOEC lines were generated, 6 from individuals with MCB and VWF levels between 30-50 IU/dL (5:1 female: male ratio, age range 11-54 years) and 2 from healthy controls (2 female, age range 22-39 years) with normal VWF levels and no symptoms of MCB.VWF Expression is decreased in Low VWF Samples: Overall transcript expression of VWF was significantly decreased in low VWF BOEC samples (5.341 transcripts/cell) vs. control endothelial cells (9.076 transcripts/cell), P <0.0001.Generalized Methylation Profiling:Via adjusted P-values, there were 129 methylation sites across multiple genes that were differentially methylated in Low VWF BOECs vs. control endothelial cells. A cluster plot demonstrates that the two control BOEC samples were generally clustered as compared to the other samples (Figure 1A).VWF Specific Methylation: The Illumina 850K array covers 70 prospective methylation sites in VWF, ranging from upstream of the transcriptional start site through the length of the gene. A previous report demonstrated that differences in 8 methylation sites in the VWF promoter correlated with VWF expression (Yuan et al. Nature Communications 2016). 7 of these sites are covered in our assay. Across all of those 7 sites, there was significant increased methylation of the CpG islands in the Low VWF BOECs when compared to the control endothelial cells (Figure 1B).Stability of VWF Methylation:To ensure that the isolation and culture of BOECS does not significantly affect the methylation status of VWF, we conducted a Pearson correlation analysis and demonstrated that peripheral leukocyte (at time of blood draw) and BOEC methylation is highly correlated at VWF specific methylation sites (R2 0.6, P = 0.0004) (Figure 1C).ConclusionsSingle cell RNA sequencing and genome wide methylation assays of BOECs from individuals with low VWF reveal significant differences in generalized methylation status when compared to BOECs from individuals with normal VWF levels and HUVECs. There is transcriptional downregulation of VWF in low VWF BOECs that is associated with hypermethylation of 7 specific VWF CpG sites in the VWF promoter. Additional sites are being evaluated. Finally, we validated the methylation status of BOECs by demonstrating high correlation with the methylation status of leukocytes from the same individuals. DisclosuresNg:Shire: Consultancy; CSL Behring: Consultancy.

Variability in Bleeding Phenotype in Type 3 VWD Families

Type 3 von Willebrand Disease (VWD) is a rare and severe form of VWD characterized by complete absence of von Willebrand factor (VWF). Patients with type 3 VWD typically present with moderate to severe mucocutaneous bleeding as well as muscle hematomas and hemarthroses. While inheritance has classically been considered autosomal recessive, there is increasing evidence for co-dominant inheritance, with heterozygous carriers affected with low VWF levels.We sought to explore the bleeding phenotype in type 3 index cases (IC) and family members (FM) enrolled in the Zimmerman Program study using the ISTH bleeding assessment tool (ISTH-BAT), and to correlate baseline bleeding score (ISTH BS) and sequence variant (SV) location as well as analyze prospective bleeding diatheses over time using an interim bleeding score (iBAT).Analysis included type 3 VWD index cases (IC), type 3 FM, type 1 affected family members (AFM) and healthy controls (HC). Clinical laboratory phenotyping was performed at BloodCenter of Wisconsin and included FVIII, VWF:Ag, VWF:RCo, VWFpp, VWF:CB3 and multimer analysis. Genotyping involved full-length VWF sequencing, array comparative genomic hybridization to detect deletions and Fabric Genomics Opal software to determine pathological variants. Bleeding symptoms were quantified using the ISTH-BAT bleeding score where baseline scores (ISTH BS) included entire history at time of enrollment and interim bleeding scores (iBAT) that represented bleeding occurring since the initial ISTH BS was obtained. Type 3 obligate carriers (OC) were defined as either having offspring with type 3 VWD or being an offspring of an individual with type 3 VWD. Type 1 AFM cohort included subjects with type 1/low VWF who were related to a type 1 IC.The type 3 families consisted of 45 unrelated type 3 IC, 56 OC with type 1/low VWF (Type 3 OC), 23 normal unaffected OC, and 8 unaffected family members (UFM). Clinical phenotyping and study entry ISTH BS are detailed in Table 1. Type 3 OC with type 1/low VWF (n=56) had mean VWF:Ag and VWF:RCo lab values which were not different from type 1/low VWF AFM (n=483) however both FVIII (68 vs 56, p<0.001) and ISTH BS (1 vs 3, p<0.0001)were both significantly different. OC without evidence of VWD (n=23) had mean VWF:Ag (79) and FVIII (122) that was significantly different (p<0.01) from healthy controls, however there was no difference in ISTH BS.The median ISTH BS in the type 3 IC was 15, with no difference between males and females. Adults had a median ISTH BS of 18 that was significantly increased (p<0.0005) compared to a score of 11 in pediatric subjects (<18). Only 1 type 3 IC did not have an abnormal BS which was an 8 year old female.No difference in ISTH BS was observed according to number of SV or between those with or without null alleles. There was also no difference in ISTH BS (13) of IC with SV in the propeptide region compared to SV in other regions of VWF (15).The highest median baseline subscores reported were hemarthorsis (3), followed by nose bleeds (2), bruising (2), and oral cavity bleeding (2) and bleeding from minor wounds (1). 17 type 3 IC had at least one follow-up visit where median total iBAT score was 11 with most bleeding due to nosebleeds, bruising, bleeding from minor wounds and oral cavity bleeding (iBAT subscores=1).Prospective bleeding was analyzed in 12 adult type 3 IC using a baseline ISTH BS cutoff of 10 to evaluate if bleeding score would predict future bleeding. 10 subjects had ISTH BS >10 (mean age 33, BS 22) and 2 had BS<10 (mean age 33, BS 10). Those with a baseline ISTH BS >10 had a median iBAT of 13 compared to those with ISTH BS<10 with an iBAT of 6, however this was not significantly different (p=0.06) most likely due to the small number of subjects.While type 3 carriers may have low VWF levels, their bleeding is mild compared to type 1 affected family members, and not significantly different from OC with normal levels. There is a difference in type 3 index case bleeding subscores from baseline study entry compared to interim bleeding most likely reflecting the effect of treatment. In this small cohort of prospective bleeding data, the baseline bleeding score did not seem to predict future bleeding as measured by the interim bleeding score. Continued prospective studies of these patients should provide valuable insight into the variability and changes in bleeding in type 3 VWD families. [Display omitted] DisclosuresMontgomery:BCW: Patents & Royalties: GPIbM assay patent to the BloodCenter of Wisconsin.

Use of Electronic Self-Administered Bleeding Assessment Tool in Diagnosis of Pediatric Bleeding Disorders

Introduction:The utility of bleeding assessment tools (BAT) as predictors of bleeding diatheses has been well established, but their utilization in the current era of electronic medical records is limited by their tediousness. Self-administered bleeding questionnaires are increasingly recognized as valid tools for guiding coagulation evaluation, shifting the onus from physicians to patients. A recent study by Casey et al evaluated use of a self-administered pediatric bleeding questionnaire (self PBQ), but the focus was on validation of the tool for screening of von Willebrand disease, and the results have not been replicated. Also, the self-PBQ, still being pen-paper based, has similar limitations as other BATs.Our study evaluates the use of an electronic version of the self-administered pediatric bleeding questionnaire through a tablet/smart device - an “eBAT”, with patients and their parents reporting the patient's bleeding symptoms prior to a hematology evaluation visit.Objectives:Primary objective was to determine the accuracy of the patient/parent self-administered eBAT by determining the level of agreement between patient/parent response and physician interview based response to the same bleeding report questionnaire (P-BAT).Methods:New patients referred to a pediatric hematology clinic for evaluation of a possible bleeding disorder were approached to participate in this study. Consenting families answered the bleeding questionnaires twice - once via a self-administered eBAT questionnaire on a tablet device via REDCap® and once through a physician administered version. The participants were randomly assigned to completing the eBAT first or the P-BAT first. The questionnaire utilized has been validated for use for minimum grade 4 reading level and patients older than 9 years of age were allowed to respond to the questionnaire themselves with help from their parents.We carried out an interim analysis as designed a priori for the study results. We assessed the correlation between eBAT and P-BAT scores and calculated the Spearman's correlation coefficient and Cochran's Kappa statistic (≥ 0.6 reflecting substantial and ≥0.9 reflecting almost perfect degrees of agreement).Results:As part of the interim analysis, we studied 48 questionnaire response pairs. Median age of subjects was 12.8 years (range: 0.04 - 20.99). The median time required for patients or parents to complete the eBAT was 6 minutes (2 - 28), with only 25% patients (n=12) requiring longer than 10 mins. There was very strong correlation of bleeding scores noted when comparing eBAT and P-BAT scores, (Spearman's correlation coefficient 0.94, Figure 1). A weighted Kappa statistic for the comparison between self eBAT and P-BAT was 0.697; indicating substantial agreement between the bleeding scores based upon physician interviews and self-reported symptoms (p-value <0.0001). On the eBAT, 75% (n=36) of patients had scores considered abnormal for children (≥3), whereas 68.8% (n=33) of patients had abnormal scores with the P-BAT (p=0.25). Out of this population, 43.8% (n=21) of patients had a specific bleeding diathesis diagnosis (von Willebrand disease or low von Willebrand factor levels, n=8, platelet function abnormality or platelet storage pool disease, n=6, other factor deficiencies, n=5 or transient coagulation abnormalities due to inhibitors, n=2). The eBAT scored per the self-PBQ based key had a sensitivity of 77.3% (95 % CI 54.6 - 92.2%), a specificity of 28% (95 % CI 12.1 - 49.4%), a positive predictive value of 48.6% (95 % CI 40.4 - 56.9%) and a negative predictive value of 58.33 % (95% CI: 34.12 - 79.10%) for identifying a bleeding disorder.Conclusions & Future Directions:In a pediatric hematology specialty clinic setting, the information gained from the eBAT was noted to be very comparable to the physician administered bleeding questionnaire in this interim analysis, with 75% of participants being able to complete the eBAT in under 10 minutes. The clinical application of eBAT has the potential to improve utilization of bleeding scores in the evaluation of patients with possible bleeding diatheses by addressing the limitations of a paper-pen based survey.Future work will focus on translating the electronic information from the eBAT to the patient medical record in real time, in the form of pertinent history data and bleeding scores. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Regulation of plasma von Willebrand factor.

Von Willebrand factor (VWF) is a multimeric plasma glycoprotein that plays a central role in the initiation of blood coagulation. Through interactions between its specific functional domains, the vascular wall, coagulation factor VIII, and platelet receptors, VWF maintains hemostasis by binding to platelets and delivering factor VIII to the sites of vascular injury. In the healthy human population, plasma VWF levels vary widely. The important role of VWF is illustrated by individuals at the extremes of the normal distribution of plasma VWF concentrations where individuals with low VWF levels are more likely to present with mucocutaneous bleeding. Conversely, people with high VWF levels are at higher risk for venous thromboembolic disease, stroke, and coronary artery disease. This report will summarize recent advances in our understanding of environmental influences and the genetic control of VWF plasma variation in healthy and symptomatic populations and will also highlight the unanswered questions that are currently driving this field of study.

Novel insights into the clinical phenotype and pathophysiology underlying low VWF levels

AbstractCritical clinical questions remain unanswered regarding diagnosis and management of patients with low von Willebrand factor (VWF) levels (30-50 IU/dL). To address these questions, the Low VWF Ireland Cohort (LoVIC) study investigated 126 patients registered with low VWF levels. Despite marginally reduced plasma VWF levels, International Society of Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH BAT) confirmed significant bleeding phenotypes in the majority of LoVIC patients. Importantly, bleeding tendency did not correlate with plasma VWF levels within the 30 to 50 IU/dL range. Furthermore, bleeding phenotypes could not be explained by concurrent hemostatic defects. Plasma factor VIII to VWF antigen (VWF:Ag) ratios were significantly increased in LoVIC patients compared with controls (P < .0001). In contrast, VWF propeptide to VWF:Ag ratios >3 were observed in only 6% of the LoVIC cohort. Furthermore, platelet-VWF collagen binding activity levels were both significantly reduced compared with controls (P < .05). In response to 1-desamino-8-D-arginine vasopressin (DDAVP), peak VWF:Ag levels exceeded 100 IU/dL in 88% of patients and was sustained >100 IU/dL after 4 hours in 72% of subjects. In conclusion, our novel data suggest that low VWF levels can be associated with significant bleeding and are predominantly due to reductions in VWF synthesis and/or constitutive secretion. Although enhanced VWF clearance may contribute to the pathophysiology in some individuals, the absolute reduction in VWF plasma half-life is usually mild and not sufficient to significantly impact upon the duration of DDAVP-induced VWF response. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

Type 2N von Willebrand disease: Characterization and diagnostic difficulties.

An abnormal factor VIII (FVIII) binding capacity of von Willebrand factor (VWF) identifies type 2N von Willebrand disease (VWD). Type 2N VWD patients are identified by means of the VWF FVIII binding (VWF:FVIIIB) assay, and especially their VWF:FVIIIB/VWF:Ag ratio (VWF:FVIIIB ratio). We report on our 15-year experience of diagnosing type 2N VWD. We have performed 2178 VWF:FVIIIB assays in bleeders and normal subjects. von Willebrand factor (VWF):FVIIIB was reduced in 682, but only 60 had low VWF:FVIIIB ratios (<0.74). Among nine patients who had a VWF:FVIIIB ratio below 0.3, four had normal VWF levels and were homozygotes for the p.R854Q mutation; the other five had low VWF levels due to a quantitative VWF mutation combined with p.R854Q. The VWF:FVIIIB ratio ranged between 0.3 and 0.73 in 51 subjects; 34 of them were heterozygotes for the p.R854Q mutation, while one carried the p.R760C. The heterozygotes for type 2N included subjects with or without bleeding symptoms, the former with significantly lower mean VWF levels than the latter. Among the 116 normal subjects tested, six were heterozygotes for the p.R854Q mutation (all asymptomatic). The prevalence of type 2N in our VWD cohort was 2.5%, and 5.2% of the general population in Northeast Italy was found heterozygous for the p.R854Q mutation. It might be difficult to reveal a type 2N defect using routine tests alone, especially when it is combined with a quantitative VWF mutation. Accordingly, we always recommend VWF:FVIIIB assay in the diagnostic workup of VWD.

Controversies in the diagnosis of Type 1 von Willebrand disease.

von Willebrand disease (VWD) is the most common bleeding disorder. Type 1 VWD represents the majority of cases and results from a partial quantitative deficiency of von Willebrand factor (VWF). The diagnosis of Type 1 VWD presents many challenges, despite there being three established diagnostic criteria: a personal history of mucocutaneous bleeding, a family history and low VWF levels. These criteria do not always coexist, and there is great overlap of clinical phenotypes and laboratory parameters between healthy individuals and those with VWD. Mild bleeding symptoms can have any number of causes and bleeding is commonly reported in the general population. VWF levels do not always correlate with bleeding symptoms and can be variable between affected family members. Additionally, VWF levels vary widely as a result of both genetic and non-genetic influences. Perhaps the greatest current controversy in the diagnosis of Type 1 VWD is that there is no consensus laboratory cut-off for the diagnosis, raising concern about both over- and under-diagnosis. Ongoing studies are addressing these issues by clarifying the underlying pathogenesis of the disease, as well as the natural history and the risk of future bleeding in those with the diagnosis.

Novel Insights into the Clinical Phenotype and Pathophysiology Underlying Low VWF Levels: The Low Von Willebrand Factor in Ireland Cohort (LoVIC) Study

▪Cohort studies have identified VWF gene mutations in ~65% of patients with type 1 Von Willebrand Disease (VWD). However, in patients with mild reductions in Von Willebrand Factor (VWF) levels, VWF mutations are less common and linkage studies suggest that the reduced plasma VWF levels are often independent of the VWFgene. Important clinical questions therefore remain unanswered regarding diagnosis and management of patients with Low VWF (levels 30-50 IU/dL). Evidence-based diagnostic criteria are needed for establishing the diagnosis of Low VWF, and the relationship between Low VWF levels and bleeding phenotype needs to be defined. Furthermore, the molecular mechanisms responsible for the reduced plasma VWF levels remain unclear. To address these questions, we established the Low VWF Ireland Cohort (LoVIC) study. In contrast to previous Type 1 VWD studies, this prospective longitudinal cohort study recruited only patients with Low VWF levels, (defined by bleeding history and lowest VWF levels 30-50 IU/dL on two occasions, three months apart) and recruited 140 adult Irish patients.Although Bleeding Assessment Tools (BATs) have been used in type 1 VWD, their utility has not been studied in patients with Low VWF. As determined using either the ISTH BAT or the Condensed MCMDM-1 VWD score, we observed significant bleeding histories in the majority of LoVIC patients. For example, among female patients (n=112), 77% had positive ISTH BAT scores (≥6) and 72% had positive MCMDM-1 scores (≥4). Importantly, bleeding tendency did not correlate with plasma VWF levels within the 30-50 IU/dL range. To further investigate this bleeding phenotype, hemostatic studies (including platelet aggregation and coagulation factor assays) were performed. Additional mild coagulation defects were identified in only 10 subjects. Furthermore, abnormal multimer patterns were identified in only 3 patients. To investigate the pathophysiology underlying Low VWF levels, plasma FVIII:C and VWF propeptide (VWF:pp) levels were defined. Interestingly, plasma FVIII:C/VWF:Ag ratios were significantly increased in LoVIC patients compared to normal controls (mean 1.3 versus 1.07; p<0.001). In contrast, increased plasma VWF:pp/VWF:Ag ratios > 3 were observed in only 6% of the total cohort. Taken together, these data demonstrate that the reduced plasma VWF levels in patients with Low VWF are predominantly attributable to decreased VWF synthesis and/or secretion rather than enhanced VWF clearance. To determine whether quantitative and/or qualitative abnormalities in platelet (plt)-VWF may influence bleeding phenotype in patients with Low VWF, we studied plt-VWF:Ag and VWF:CB in 50 consecutive LoVIC patients. In keeping with the hypothesis that reduced VWF synthesis plays a key role in the pathogenesis underlying Low VWF levels, plt-VWF:Ag and plt-VWF:CB levels were both significantly reduced in LoVIC patients compared to controls (mean plt-VWF:Ag 0.16 versus 0.21 IU/109/L, p<0.05; mean plt-VWF:CB 0.18 versus 0.34 IU/109/L, p<0.001).To further study the molecular mechanisms underlying Low VWF levels, plasma VWF:Ag and VWF:RCo responses following desmopressin (DDAVP) administration were examined. In 88% of patients, the post-DDAVP peak levels exceeded 100 IU/dL. Importantly, the response to DDAVP was also sustained with both VWF:Ag and VWF:RCo above 100 IU/dL after 4 hours in 72% subjects. These DDAVP responses demonstrate that Weibel Palade body stores of VWF are maintained in patients with Low VWF, and that the regulated pathway of VWF secretion is intact. Furthermore, the sustained plasma VWF response observed following DDAVP supports the hypothesis that enhanced VWF clearance does not play a major role in the pathogenesis of Low VWF levels.In conclusion, we demonstrate that Low VWF levels are associated with a significant bleeding phenotype. In addition, we further show that in the majority of patients with Low VWF levels, the bleeding phenotype cannot be explained by the presence of concomitant bleeding disorders. Finally, our novel data demonstrate that Low VWF levels are due in large part to reductions in VWF synthesis and/or constitutive secretion. Although enhanced VWF clearance may contribute to the pathophysiology in a minority of individuals with Low VWF, the absolute reduction in VWF plasma half-life is usually mild and not sufficient to significantly impact upon the duration of DDAVP-induced VWF response. DisclosuresLavin:Baxalta: Consultancy, Research Funding. O'Sullivan:Pzifer: Research Funding. O'Connell:Baxalta: Consultancy, Research Funding. James:Octapharma: Research Funding; Bayer: Research Funding; CSL Behring: Research Funding; Biogen: Consultancy; Basalt: Consultancy. Di Paola:CSL BEhring: Consultancy; Biogen: Consultancy. O'Donnell:Bayer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novo Nordisk: Research Funding, Speakers Bureau; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Leo Pharma: Speakers Bureau; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees.

No Association Between Normalization of VWF Levels and Bleeding Phenotype in Patients with Type 1 VWD - from the Win Study

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. We included patients from the nationwide cross-sectional "Willebrand in the Netherlands" Study, with lowest historical VWF antigen (VWF:Ag) and/or VWF activity (VWF:Act) ≤30 U/dL. At inclusion, blood was sampled for central measurement of VWF:Ag and VWF:Act and VWF to collagen binding (VWF:CB). Central measurements were available in 367 type 1 VWD patients. Based on these central measurements, patients were divided into three groups: definite VWD (central VWF:Ag and/or VWF:Act and/or VWF:CB ≤30 U/dL, n=152); low VWF (central VWF:Ag and/or VWF:Act and/or VWF:CB 31-50 U/dL , n=120) and historical VWD with presently normalized levels (central VWF:Ag and VWF:Act and VWF:CB ≥51 U/dL, n=95). Age differed between groups: median age was 43 years in definite VWD patients, 45 years in low VWF and 50 years in historical VWD patients (p VWF gene was most common in definite VWD patients: 55/76 (72%) patients in whom mutation analysis was performed had a variant compared with 22/41 (54%) low VWF and 13/41 (32%) historical VWD patients (p Median Tosetto Bleeding Score (BS) did not differ between the three groups as it was respectively 9, 8 and 9 in definite VWD patients , low VWF patients and historical VWD patients (p=NS), see table 1. The incidence of bleeding episodes requiring treatment with desmopressin or clotting factor concentrate in the year prior to inclusion also did not differ between groups as it was 18% in definite VWD, 22% in "low VWF" and 27% in historical VWD patients (p=NS). In many countries VWF levels 60 IU/dL are used as the cut-off value for abnormal VWF levels. Using this value as cut-off between low VWF and historical VWD, 151 (42%) patients had low VWF and 64 (17%) patients had historical VWD. Using this cut-off value had no major effect on bleeding phenotype or patient characteristics (data not shown). In conclusion, patients with higher VWF levels at the time of study were older and less often had a variant in the VWF gene. More historical VWD patients were index cases, underlining their negative family history. In contrast, blood group O was more common in patients with normalized VWF levels, suggesting that factors outside the VWF gene have a more important effect on VWF levels in this group. Importantly, the bleeding score was similar in all groups. The bleeding score is a reflection of bleeding symptoms that have occurred throughout one9s life and may therefore not detect changes in bleeding phenotype over time. Importantly, the bleeding incidence requiring treatment in the year prior to inclusion was also similar in all groups, regardless of VWF levels. Our study suggests that normalization of VWF levels is not associated with the bleeding phenotype in type 1 VWD patients. However, this study is limited by its retrospective design and prospective studies are required to assess the bleeding phenotype and bleeding rate in more detail and to identify patients at increased or decreased risk of bleeding. 1 Sanders YV, Giezenaar MA, Laros-van Gorkom BA, et al. von Willebrand disease and aging: an evolving phenotype. J Thromb Haemost . 2014;12(7):1066-1075. Disclosures Boender: CSL Behring: Research Funding. Eikenboom: CSL Behring: Research Funding. Fijnvandraat: CSL Behring: Research Funding; Bayer: Research Funding. Meijer: Bayer: Honoraria, Research Funding; Baxter: Research Funding; Pfizer: Research Funding; Sanquin: Honoraria, Research Funding; Boehringer Ingelheim: Honoraria; Bristol-Myers Squibb: Honoraria. Mauser-Bunschoten: Baxter: Research Funding; Bayer: Research Funding; CSL Behring: Research Funding; Novo Nordisk: Research Funding; Griffols: Research Funding; Sanquin: Research Funding. Cnossen: Novo Nordisk: Research Funding; CSL Behring: Other: Travel Funding, Research Funding; Pfizer: Research Funding; Novartis: Research Funding; Baxalta: Research Funding; Bayer: Research Funding. Laros-van Gorkom: CSL Behring: Research Funding. van der Bom: CSL Behring: Research Funding; Novo Nordisk: Research Funding; Pfizer: Research Funding; Bayer: Research Funding; Baxalta: Research Funding. Leebeek: UniQure: Consultancy; Netherlands Hemophilia Foundation: Research Funding; Baxter: Research Funding; CSL Behring: Research Funding.

Von Willebrand Factor to Prevent Postpartum Hemorrhage

Background: Von Willebrand disease (VWD) is the most common inherited bleeding disorder and is characterized by deficient and/or defective von Willebrand factor (VWF) which results in spontaneous and traumatic mucosal bleeding. In women with VWD, pregnancy is associated with excess blood loss and poor quality of life. Recently, a prospective cohort study by James et al Haemophilia 2015, determined that even when treatment is given, women with VWD had lower VWF levels, greater blood loss at delivery, and lower hematocrit than controls without VWD. The reason for this finding remains unknown. Current VWF dosing is weight-based, but does not account for the ~1.4-1.5-fold increase in blood volume during pregnancy. To address this, we conducted a feasibility study for a prospective, randomized phase III trial comparing weight-based, 50 IU/kg, with volume-based, 80 IU/kg, VWF to prevent postpartum hemorrhage (PREVENT PPH Trial). Methods: To establish trial feasibility: 1) we compared pre-pregnancy and 8th-month VWF levels in women with VWD with and without PPH (≥500 cc blood loss in the 1st 24 hours) following vaginal delivery; 2) we evaluated VWF dosing in women with PPH in the James study; 3) we assessed thrombosis risk and VWF concentrate dose by literature review; 4) we surveyed current practice regarding VWF concentrate use at delivery by U.S. hemophilia treatment center (HTC) MDs; and 5) we conducted structured interviews of MDs and VWD patients to determine trial acceptability. Analysis was by Student9s t-test for continuous data, and Fisher9s exact test for discrete data. Results:In the Retrospective VWD-PPH Study of 16 women with VWD (14 type 1; 2 type 2) undergoing vaginal delivery, PPH was associated with higher pre-delivery weight, pre: 88.1 vs. 67.6 kg; 8thmonth: 99.9 vs. 75.0 kg; and delivery: 104.0 vs. 78.6 kg, all p Conclusions: The findings of this feasibility study indicate that pre-pregnancy VWF:RCo may be a better predictor of PPH than 8thmonth VWF:RCo. High pre-delivery weight which is associated with high blood volume may increase PPH, possibly through dilution of VWF levels. A VWF dose of ~50 IU/kg, which is the first line of therapy at delivery and the current standard of practice, may not prevent PPH. Thrombosis risk with VWF in published studies is low even at doses >80 IU/kg. Drug safety, local obstetric collaboration, and coverage of staff, travel, and childcare costs are critical issues to address in trial design. Disclosures Ragni:SPARK: Research Funding; Genentech: Research Funding; Tacere Benitec: Consultancy; Vascular Medicine Institute: Research Funding; OPKO: Research Funding; Novo Nordisk: Research Funding; Alnylam Pharmaceuticals: Consultancy, Research Funding; Baxalta: Research Funding; Biogen: Consultancy, Research Funding; Biomarin: Consultancy; Shire: Consultancy; CSL Behring: Research Funding. James:Intramural University of Ghana Research Fund: Research Funding; Vanderbilt University Medical Center Gift Funds: Research Funding. Malec:Biogen: Consultancy; Vascular Medicine Institute: Research Funding; Biogen: Research Funding; Baxalta: Research Funding. Kessler:Octapharma: Consultancy, Research Funding; Novo Nordisk: Consultancy, Research Funding; Grifols: Consultancy; Genentech: Consultancy, Research Funding; Biogen: Consultancy; Bayer: Consultancy, Research Funding; Pfizer: Consultancy; Baxalta: Consultancy, Research Funding; LFB: Other: Member of DSMB. Kouides:CSL Behring: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Baxalta: Consultancy. Neff:Shire: Membership on an entity9s Board of Directors or advisory committees; Pfizer: Other: DSMB Chair for research study; ABIM: Other: Hematology Exam committee; CSL Behring: Membership on an entity9s Board of Directors or advisory committees; HEMA Biologics: Membership on an entity9s Board of Directors or advisory committees. Philipp:Novo Nordisk: Membership on an entity9s Board of Directors or advisory committees; Baxalta: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Merck: Other: Data Safety Monitoring Board. Brooks:Gilead Sciences: Research Funding.

Monitoring Therapy during Treatment of von Willebrand Disease.

von Willebrand factor (VWF) is an adhesive plasma protein that primarily acts to bridge platelets to sites of vascular injury and thus prevent bleeding. von Willebrand disease (VWD) is the most common inherited bleeding disorder and is caused by deficiency and/or defects of VWF, leading to low levels of plasma VWF or dysfunctional VWF. Factor VIII (FVIII) is also reduced in many patients with VWD, since VWF stabilizes and protects FVIII from degradation. Treatment of VWD primarily entails replacement of VWF, and sometimes FVIII, to protect against bleeding. This may entail use of VWF/FVIII concentrates, and/or desmopressin (1-deamino-8-d-arginine vasopressin) to release endogenous VWF in some patients. Adjunct therapies include antifibrinolytics and hormonal therapies in women. Optimal treatment of VWD entails measuring the effects of treatment, either as a trial before surgery or during therapeutic management. This is usually accomplished by performance of the same tests that are used to help diagnose VWD, although additional monitoring (clinically and/or by laboratory testing) may also be performed. The current review provides an overview of the treatment of VWD but is primarily focused on the monitoring of such therapy.