Low Von Willebrand Factor Levels Research Articles

Shiga toxin down-regulates ERG protein in endothelial cells and impairs angiogenesis

BackgroundShiga toxin (Stx) can activate inflammatory signaling, leading to vascular dysfunction and promotion of a pro-thrombotic tissue microenvironment. Stx can trigger the development of the enterohemorrhagic (childhood) hemolytic uremic syndrome (eHUS), a triad of thrombocytopenia, hemolytic anemia, and acute kidney injury, often requiring dialysis. Additional features may include damage to other organs, including the gastrointestinal tract, pancreas, brain and cardiovascular system; death occurs in 2–5 %. eHUS is a thrombotic microangiopathy; thus, endothelial cell (EC) injury and platelet fibrin thrombus formation in glomerular arterioles and in the arterioles of other affected organs are likely. To elucidate mechanisms of this microangiopathy, we examined in human ECs the regulation of the platelet adhesion proteins P-selectin and von Willebrand factor (VWF), along with the downregulation of erythroblast-transformation-specific transcription factor (ERG) a key regulator of angiogenesis and megakaryocyte development. MethodsVWF, P-selectin, and ERG levels were determined using immunofluorescence and Western blot in human umbilical endothelial cells (HUVECs). HUVECs were treated with tumor necrosis factor-alpha (TNF-α), Stx-1 or both, versus normal controls. Capillary morphogenesis on Matrigel was performed using HUVECs treated, for 22 h with TNF-α, Stx-1, or both, or treated 4 h with Stx-1 alone or in combination with TNF-α for 22 h. ResultsStx-1 significantly reduced ERG and VWF expression on HUVECs, but upregulated P-selectin expression. ERG levels decreased with Stx-1 alone or in combination with TNF-α, in the nuclear, perinuclear and cytoplasmatic regions. Stx-1 reduced capillary morphogenesis, while Stx-1-TNF-α combined treatment reduced capillary morphogenesis still further. ConclusionsIn the presence of Stx-1 or TNF-α or both treatments, ECs were activated, expressing higher levels of P-selectin and lower levels of VWF. Our findings, further, provide evidence that Stx-1 downregulates ERG, repressing angiogenesis in vitro.

Key Drivers of Coagulation Factor Use in Von Willebrand Disease During Hospitalization: An Overview of the French BERHLINGO Cohort.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. However, studies of hospitalisation patterns with replacement treatment are scarce. The aim of this study was to investigate the current therapeutic management of VWD and determine the key drivers of coagulation factor uses in patients during hospitalisation. Hopscotch-WILL was a multi-centric retrospective study conducted over a 48-month period in any patients with VWD. The data were collected from the BERHLINGO Research Database and the French Hospital database. A total of 988 patients were included; 153 patients (15%) were hospitalised during 293 stays requiring treatment with von Willebrand factor (VWF) concentrates-pure or in association with Factor VIII (FVIII). Their median basal concentrations of VWF and FVIII were significantly lower than in untreated patients: VWF antigen < 30 IU/dL, VWF activity < 20 IU/dL and FVIII:C < 40 IU/dL. The median (interquartile range) concentrate consumption was similar between highly purified VWF or VWF combined with FVIII (72 [110] vs 57 [89] IU/kg/stay, p = 0.154). The use of VWF was highly heterogeneous by VWD type; type 3 had a particularly high impact on VWF consumption in non-surgical situations. The main admissions were for ear/nose/throat, hepato-gastroenterology, and trauma/orthopaedic conditions, besides gynaecological-obstetric causes in women. The use of VWF concentrates is mostly influenced by low basal levels of VWF and FVIII, but also by VWD type or the cause for hospitalisation. These results could inform future studies of newly released recombinant VWF.

Impact of Blood Group O and Von Willebrand Factor on Bleeding Severity in Patients with Von Willebrand Disease and Bleeding Disorder of Unknown Cause

Background: In patients with bleeding, von Willebrand disease (VWD) is diagnosed at von Willebrand factor (VWF) levels of ≤50 IU/dL ( James et al. Blood Adv. 1:280-300. 2021). Nevertheless, the majority of patients with a mild to moderate bleeding disorder (MBD) is diagnosed with bleeding disorder of unknown cause (BDUC), upon exclusion of VWD, platelet function defects (PFD), and coagulation factor deficiencies (CFD). Bleeding severity in patients with VWD does not correlate well with VWF levels in type 1 VWD, suggesting other modifiers of the bleeding tendency, when patients with severe VWD are excluded. Blood group O (BG O) is associated with lower VWF levels and has been found to be overrepresented in VWD. In BDUC patients, BGO is also overrepresented and recognized as an independent risk factor for bleeding severity and recurrent bleeding ( Mehic et al. Blood Adv.20: 5157-5164. 2020; Mehic et al. JTH. 7: 1757-1768. 2023). Aim: This study aimed to comprehensively investigate the clinical phenotype of patients with VWD or BDUC from the Vienna Bleeding Biobank (VIBB) and evaluate the direct effect of ABO BG on bleeding severity beyond its effect on VWF levels. Methods: Patients with VWD or BDUC from the VIBB, a single-center cohort study (EC 603/2009), were categorized by lowest VWF, as measured by VWF:antigen (VWF:Ag) or VWF ristocetin co-factor activity (VWF:RCo), into four groups: &amp;lt;30 IU/dL (very low VWF), 30-50 IU/dL (low VWF), 51-80 IU/dL, and &amp;gt;80 IU/dL. Patients diagnosed with PFD (n=221), CFD (n=28), or other diagnoses (n=4) were excluded. To study the association of BG O with bleeding severity irrespective of VWF levels, we fitted linear regression models adjusting for age, sex, and lowest VWF. We allowed for non-linearity by modelling age and sex with restricted cubic splines. Results: A total of 637 patients, 18 (2.8%) with very low VWF, 55 (8.6%) with low VWF, 237 (37.2%) with VWF levels ranging from 51 to 80 IU/dL and 327 (51.3%) with VWF levels &amp;gt;80 IU/dl, were included in this analysis, as summarized in Table 1. BG O was more prevalent in patients with very low VWF levels (61%), low VWF levels (71%), and VWF levels 51-80 IU/dL (66%) than in patients with VWF levels &amp;gt;80 IU/dL (30%). Patients with low VWF were youngest, followed by very low VWF and those with VWF 51-80 IU/dL. Age was highest in the patient group with VWF levels &amp;gt;80 IU/dL at clinical presentation and might influence VWF levels and bleeding scores. With regard to bleeding severity, patients with very low VWF levels had highest median bleeding scores or number of bleeding manifestations, while the bleeding severity was similar amongst the other three categories (Table 1). VWF levels did not correlate with bleeding severity scores (Vicenza score: Spearman rho=-0.03, p=0.53; ISTH BAT: rho=-0.02, p=0.75; number of bleeding manifestations: rho=-0.02, p=0.66). In linear regression, holding age, sex, and lowest VWF levels constant, predicted mean bleeding scores and number of bleeding manifestations were higher with BG O (Vicenza score mean difference [MD], 0.64; 95% confidence interval [95%CI], 0.12 to 1.25; p=0.015; ISTH BAT MD 0.52; 95%CI, -0.25 to 1.28; p=0.18; number of bleeding manifestations MD, 0.24; 95%CI, -0.06 to 0.54; p=0.12) (Figure 1). Conclusion: Our findings demonstrate an overlap between VWD and BDUC with a similar clinical phenotype and bleeding phenotype, but increased severity in patients with VWF levels &amp;lt;30 IU/dL. Patients with BG O had increased bleeding scores compared to those with BG non-O. BG O appears to be an independent factor in modifying bleeding severity in both patients with VWD or BDUC across all VWF ranges.

Clinical and Laboratory Presentation and Underlying Mechanism in Patients with Low VWF.

Low von Willebrand factor (VWF) refers to subjects with plasma levels of 30 to 50 IU/dL. The mechanism of low VWF is poorly understood. We chose to determine the clinical presentation, laboratory phenotype, and underlying mechanisms of low VWF. We included 250 patients characterized with low VWF. The International Society on Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH-BAT) was used to assess clinical symptoms. To determine the underlying mechanisms of low VWF, we used as markers the VWF propeptide (VWFpp) assay and FVIII:C/VWF:Ag ratio for VWF synthesis and the VWFpp/VWF:Ag ratio for VWF clearance. Results were compared with those of 120 healthy controls. Cases with abnormal screening tests were further evaluated for coagulation factor levels and platelet disorders. The median age of the cohort was 35 years (range 3-85), 21% were children (n = 53), 34% were adult males (n = 85), and 45% (n = 112) were adult females. According to the ISTH-BAT, abnormal bleeding was found in 35% of children, 47% of males, and 49% of females. No association was found between VWF activity levels and ISTH-BAT. Patients showed an overall decreased VWF synthesis/secretion and an enhanced VWF clearance was identified in 33% of them. In 89 patients (36%), there were other hemostasis-related defects, but there was no difference in the ISTH-BAT between the two groups. Our findings indicate that reduced VWF synthesis/secretion and enhanced VWF clearance are major mechanisms of low VWF levels. Patients with low VWF have significant bleeding manifestations. While other hemostasis defects occurred together with low VWF, this combination did not exacerbate clinical symptoms.

Initial von Willebrand factor antigen values in adolescent females predict future values.

Diagnosing von Willebrand Disease (VWD) in adolescent females is challenging as menstruation and physiologic stress elevate von Willebrand factor (VWF) laboratory values. To develop a VWF prediction model for adolescent females based on initial VWF results. We identified female patients aged 9 to 21 years with any VWF laboratory test over a 5-year period (2017-2021) at any Texas Children's Hospital facility. Patient demographics, VWF testing, haemoglobin concentration, serum ferritin and site of clinical testing were collected (initial and subsequent laboratory evaluations). A Bayesian linear regression model was developed. Prediction intervals were analysed to identify thresholds for patients in whom repeat testing was unlikely to identify low VWF levels (<50%), consistent with VWD. A total of 6125 adolescent females underwent VWF testing; 1204 (19.7%) had repeat testing. Based on the prediction model, initial VWF antigen values of 80%, 90% and ≥100% carried a 92.6%, 96.6% and ≥98.0% probability of having repeat normal repeat VWF values, respectively.Subjects assessed in outpatient adolescent medicine or gynaecology clinics were more likely to have low VWF values compared to those assessed in the acute care setting (p<.001). Median presenting haemoglobin and serum ferritin were 12.4g/dL and 13ng/mL, respectively and were similar in those with normal versus low VWF antigen values. Repeat testing in adolescent females whose initial VWF antigen values are ≥90% is unlikely to identify additional patients with VWD. Iron deficiency screening should be performed in all adolescent females.

Impact of ABO Blood Group on Thromboembolic and Bleeding Complications in Patients with Left Ventricular Assist Devices.

The ABO blood group system is linked to hemostasis via its relationship with von Willebrand factor (VWF) and factor VIII (FVIII). In the current study, we investigated the association of the ABO system with clinical outcomes as well as VWF and platelet function in patients with left ventricular assist devices (LVADs). Bleeding and thromboembolic complications were assessed in 111 patients during 1 year after LVAD implantation. In 67 LVAD patients, VWF antigen, VWF activity, VWF ristocetin cofactor, VWF collagen-binding, and FVIII activity were assessed. Platelet surface P-selectin and activated glycoprotein IIb/IIIa were determined by flow cytometry, and soluble P-selectin was measured with an enzyme-linked immunoassay. Platelet aggregation was assessed by light transmission and impedance aggregometry. Thirty-six patients (32.4%) experienced a bleeding and 22 patients (19.8%) a thromboembolic event. In univariate analyses, patients with blood group O had numerically more bleeding complications and less thromboembolic events as compared to patients with blood group non-O (both p ≥ 0.05). After multivariable adjustment, blood group O was significantly associated with a higher risk of bleeding (hazard ratio 2.42 [95% confidence interval 1.03-5.70], p = 0.044) but not linked to thromboembolic complications. Patients with blood group O had significantly lower levels of VWF and FVIII (all p < 0.05), whereas P-selectin expression in response to thrombin-receptor activating peptide and soluble P-selectin were higher as compared to patients with blood group non-O (both p < 0.05). LVAD patients with blood group O are at an increased bleeding risk, potentially due to lower VWF and FVIII levels.

QUALITY OF LIFE OF PATIENTS WITH VON WILLEBRAND DISEASE

von Willebrand disease (VWD) is the most common bleeding disorder due to a qualitative or quantitative disorder of von Willebrand Factor (VWF). There are three main types of the disease (types 1, 2, and 3) and a total of 6 subgroups. Type 1 patients present low levels of VWF; type 2 patients present low activity of VWF, and type 3 patients have a virtual absence of this VWF. VWD is the most common coagulopathy in the human population, but is the least diagnosed. Undiagnosed individuals may present symptoms that are often neglegted. The aim of this study was to analyze the quality of life of patients with VWD who are treated at Fundação Hemominas. Patients were invited to participate in consultations and examinations. The 30 patients included (17 women and 13 men) answered a 36-item brief health questionnaire (SF-36). The analysis of quality of life in women showed that the concept of physical functioning received a median (MED) of 82.5% (IQR 73.8%-95%); the concept of role limitations due to physical health received a MED of 100% (IQR 18.8%-100%); the concept of pain received MED of 61% (IQR 61%-84%); the concept of general health received MED of 77% (IQR 60.8%-88.3%); the concept of energy/fatigue received MED of 57.5% (IQR 33.8%-80%); the concept of social functioning received MED of 81.5% (IQR 25%-100%); the concept of emotional well-being received MED of 83.5% (IQR 33%-100%); and the concept of mental health received MED of 76% (IQR 34%-80%). In men, on the other hand, the analysis of quality of life showed that the concept of physical functioning received a MED of 90% (IQR 70%-100%); concept of role limitations due to physical health received a MED of 25% (IQR 0%-75%); the concept of pain received MED of 72% (IQR 50%-84%); the concept of general health received MED of 67% (IQR 47%-85%); the concept of energy/fatigue received MED of (IQR 50%-80%); the concept of social functioning received MED of 75% (IQR 38%-75%); the concept of emotional well-being received MED of 100% (IQR 67%-100%); and the concept of mental health received MED of 80% (IQR 68%-84%). After analyzing these data, it was not possible to find a significant difference between male and female patients. In conclusion, our study is important to better understand which aspects of quality of life are most impaired in patients with VWD. This study has some limitations because patients were not subdivided by VWD type, and no participants were genotyped yet. This is an ongoing study and the number of participants needs to be increased to draw conclusions. We thank all participants, Fapemig, Fundação Hemominas, and the CGSH of the Ministry of Health.

Microsurgical Breast Reconstruction in Patients with Disorders of Hemostasis: Perioperative Risks and Management.

Surgical and technological advances have resulted in the widespread adoption of microsurgical breast reconstruction. Many comorbidities that potentially might impair vasculature and wound healing are no longer considered contraindications for these procedures. However, some uncertainty still prevails regarding the perioperative management of patients with disorders of hemostasis. The authors combined a literature review with a retrospective chart review of patients with disorders of hemostasis who had undergone microsurgical breast reconstruction at the senior author's (J.F.) center between 2015 to 2020. Several disorders associated with thrombotic and/or hemorrhagic complications were identified, and a standardized risk assessment and management strategy was developed in cooperation with a hematologist. Overall, 10 studies were identified comprising 29 patients who had a defined disorder of hemostasis and underwent microsurgical breast reconstruction. Seventeen microsurgical breast reconstructions were performed on 11 patients at the senior author's (J.F.) center. High factor VIII levels, heterozygous factor V Leiden, and heterozygous prothrombin mutation G20210A were the most common genetic or mixed genetic/acquired thrombophilic conditions. As expected, hereditary antithrombin, protein C, or protein S deficiencies were rare. Among hemorrhagic disorders, thrombocytopenia, platelet dysfunction, and von Willebrand disease or low von Willebrand factor levels were those factors most frequently associated with increased perioperative bleeding. Patients should be screened for elevated risk of thrombosis or bleeding before undergoing microsurgical breast reconstruction, and positive screening should prompt a complete hematologic evaluation. Interdisciplinary management of these disorders with a hematologist is essential to minimize risks and to obtain optimal reconstructive results. Risk, IV.

Phenotypic and Genotypic Signatures of VWF Exon 18 in Eastern Saudi Patients Previously Diagnosed with Type 1 von Willebrand Disease.

Introductionvon Willebrand disease (VWD) is the most prevalent bleeding disease, which is associated with either low levels of von Willebrand factor (VWF) or abnormality in its structure. Three types of the disease have been described; type 1 (VWD1) and 3 (VWD3) are caused by deficiency of VWF and type 2 (VWD2) is caused by production of defective VWF. The aim of the current study was to characterize gene variants of VWF gene; exon 18 in particular, in a cohort of Saudi families as well as healthy control subjects.MethodsA total of 19 families comprising 60 subjects of type 1 VWD were enrolled in the study. Participants were divided into 22 index cases, 21 affected family members and 17 unaffected family members ranging in age from 6 to 70 years. Blood samples were collected from all participants to measure activated partial thromboplastin time test (APTT), von Willebrand antigen level (VWF:Ag), Factor VIII activity (FVIII:C) and ristocetin cofactor activity (VWF:RCo), platelet count, determining the ABO blood group and for genetic analysis by Sanger sequencing.ResultsThe results indicated that VWD1 patients have lower levels of VWF and factor VIII than the non-affected family members and the control subjects. In addition, five gene variants were reported in VWF exon 18; of these, c.2365A>G and c.2385T>C were more common in the control group and might be protective from VWD.DiscussionIn conclusion, VWF levels are influenced by blood group, and there was no association between variants in exon 18 of VWF gene reported in all groups and the disease status; however, blood group analysis and genome-wide genotyping could help to highlight high-risk groups and improve clinical management of VWD.

Dispatch and delivery at the ER-Golgi interface: how endothelial cells tune their hemostatic response.

Von Willebrand factor (VWF) is a glycoprotein that is secreted into the circulation and controls bleeding by promoting adhesion and aggregation of blood platelets at sites of vascular injury. Substantial inter-individual variation in VWF plasma levels exists among the healthy population. Prior to secretion, VWF polymers are assembled and condensed into helical tubules, which are packaged into Weibel-Palade bodies (WPBs), a highly specialized post-Golgi storage compartment in vascular endothelial cells. In the inherited bleeding disorder Von Willebrand disease (VWD), mutations in the VWF gene can cause qualitative or quantitative defects, limiting protein function, secretion, or plasma survival. However, pathogenic VWF mutations cannot be found in all VWD cases. Although an increasing number of genetic modifiers have been identified, even more rare genetic variants that impact VWF plasma levels likely remain to be discovered. Here, we summarize recent evidence that modulation of the early secretory pathway has great impact on the biogenesis and release of WPBs. Based on these findings, we propose that rare, as yet unidentified quantitative trait loci influencing intracellular VWF transport contribute to highly variable VWF levels in the population. These may underlie the thrombotic complications linked to high VWF levels, as well as the bleeding tendency in individuals with low VWF levels.

Influence of blood group and von Willebrand factor on population pharmacokinetics and dose individualization of recombinant factor VIII in Taiwanese patients with haemophilia A.

The large interpatient variability in the pharmacokinetic (PK) parameters of recombinant Factor VIII (rFVIII) observed in haemophilia A hinders efficient and cost-beneficial prophylactic regimen initiation. Identification of factors influencing the PK of rFVIII may shed more light on personalised treatment. This study aimed to develop a population PK model in the Taiwanese haemophilia A and evaluate the current national health insurance (NHI) reimbursement guidelines of Taiwan for haemophilia treatment. A population PK analysis was established based on 69 Taiwanese with moderate or severe haemophilia A. A nonlinear mixed-effects modelling (NONMEM® ) was used to estimate PK parameters and their variabilities. A Monte Carlo simulation was performed to evaluate different prophylactic regimens. A two-compartment model with first-order elimination best described the rFVIII data. Weight-based allometric scaling was related to clearance and central volume of distribution. Blood type and baseline von Willebrand factor (VWF) were significant covariates for clearance. For single dose simulations, a time achieving target level (>1IU/dL) was associated with increasing rFVIII dose and VWF level. The multiple dose simulations showed that>96.4% of patients with high VWF level (>200%) had predicted trough level>1IU/dL for all dosing regimens (15-40IU/kg, two to three times weekly). However, for twice weekly dosing, lower percentage (47.62-62.20%) of patients with blood group O and low VWF level (<50%) achieved a predicted trough level>1IU/dL. The population PK of rFVIII was successfully developed. Dose adjustment based on blood type and VWF level should be considered.

Whole-exome analysis of adolescents with low VWF and heavy menstrual bleeding identifies novel genetic associations

AbstractAdolescents with low von Willebrand factor (VWF) levels and heavy menstrual bleeding (HMB) experience significant morbidity. There is a need to better characterize these patients genetically and improve our understanding of the pathophysiology of bleeding. We performed whole-exome sequencing on 86 postmenarchal patients diagnosed with low VWF levels (30-50 IU/dL) and HMB and compared them with 660 in-house controls. We compared the number of rare stop-gain/stop-loss and rare ClinVar “pathogenic” variants between cases and controls, as well as performed gene burden and gene-set burden analyses. We found an enrichment in cases of rare stop-gain/stop-loss variants in genes involved in bleeding disorders and an enrichment of rare ClinVar “pathogenic” variants in genes involved in anemias. The 2 most significant genes in the gene burden analysis, CFB and DNASE2, are associated with atypical hemolytic uremia and severe anemia, respectively. VWF also surpassed exome-wide significance in the gene burden analysis (P = 7.31 × 10−6). Gene-set burden analysis revealed an enrichment of rare nonsynonymous variants in cases in several hematologically relevant pathways. Further, common variants in FERMT2, a gene involved in the regulation of hemostasis and angiogenesis, surpassed genome-wide significance. We demonstrate that adolescents with HMB and low VWF have an excess of rare nonsynonymous and pathogenic variants in genes involved in bleeding disorders and anemia. Variants of variable penetrance in these genes may contribute to the spectrum of phenotypes observed in patients with HMB and could partially explain the bleeding phenotype. By identifying patients with HMB who possess these variants, we may be able to improve risk stratification and patient outcomes.

Preoperative bleeding risk assessment with ISTH-BAT and laboratory tests in patients undergoing elective surgery: A prospective cohort study.

Patients with inherited haemorrhagic disorders may bleed during surgery. No questionnaire on bleeding diathesis has been yet validated for the preoperative period and current guidelines provide conflicting recommendations. We aimed to assess if preoperative assessment with ISTH-BAT (International Society on Thrombosis and Haemostasis Bleeding Assesment Tool) and laboratory screening tests is useful to identify mild previously undiagnosed bleeding disorders (BDs) and to predict bleeding complications in selected patients undergoing elective surgery. Consecutive patients undergoing elective surgery received ISTH-BAT evaluation and laboratory screening for platelet count, Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT). Subjects with an abnormal ISTH-BAT and/or laboratory results underwent further testing, and they were compared with a 1:1 random gender-, age- and type of surgery- matched control group. Overall, 1502 consecutive surgical patients (1186 adults, 316 children) were enrolled. Of these, 83 (5.5%, 95% confidence interval 4.4-6.8) patients (37 adults and 46 children) had an abnormal ISTH-BAT, and/or prolonged PT and/or prolonged aPTT and/or low platelet count; of them, one subject had low von Willebrand factor level, three Factor XII deficiency and four anticardiolipin and/or antiB2GPI antibodies. No major bleeding was reported in these 83 patients and their controls. ISTH-BAT and laboratory screening tests do not accurately detect mild BDs in selected patients undergoing elective surgery.

ABO blood groups do not predict progression of traumatic intracranial hemorrhage

ABO blood groups are associated with genetically predisposed variations in von Willebrand factor (VWF) resulting in higher risks of thrombotic events in non-O blood types and bleeding complications in blood type O. The role of ABO blood groups in progression of traumatic intracranial hemorrhage (TICH) is unknown. Given statistically lower VWF levels in blood type O in the general population, we hypothesized that blood type O patients have a higher risk of such progression. A retrospective review of adult trauma patients with isolated TICH admitted to a Level 1 trauma center over eight years was conducted. Patients were categorized with blood type O and non-O (types A, B, AB) delineation. The primary outcome was radiological progression of TICH during the first 24 h. Secondary outcomes included surgical intervention after follow-up computed tomography (CT), complications, days on mechanical ventilation (DMV), intensive care unit (ICU) length of stay (LOS), hospital LOS, and mortality. Of 949 patients, 432 (45.5%) had blood type O. When comparing O and non-O groups, no significant differences were found in gender, age, race, admission vital signs, Glasgow Coma Scale, coagulation profile, TICH type, or Injury Severity Score. No difference in TICH progression was found between O and non-O groups: 73 (17%) vs 80 (15%), respectively, p = 0.55. Blood type O mortality was 12 (3% vs. 23 (4%), p = 0.174). Rate of TICH surgical intervention after follow-up CT, DMV, complications, and ICU and hospital LOS did not differ. No association between ABO blood types and radiological progression of TICH was identified.

Elevated von Willebrand factor levels during heavy menstrual bleeding episodes limit the diagnostic utility for von Willebrand disease

BackgroundHeavy menstrual bleeding (HMB) is often the first bleeding symptom for female individuals with inherited bleeding disorders. Guidelines recommend performing the hemostatic evaluation at HMB presentation. Von Willebrand factor (VWF) levels increase with stress, making it unclear if VWF studies during acute bleeding are beneficial in diagnosing von Willebrand disease (VWD). ObjectivesTo determine the utility of testing for VWD during acute HMB. Patients/MethodsThis retrospective cohort study evaluated VWF levels of individuals presenting to the emergency department (ED) with HMB from January 1, 2017, to December 31, 2018, after prospective implementation of a clinical practice guideline recommending hemostatic evaluation in the ED. We compared VWF and factor VIII (FVIII) levels between acute presentation and follow‐up visit after bleeding resolution. We compared the diagnostic accuracy of initial and follow‐up labs. ResultsDuring the study period, 221 individuals were seen in the ED for acute HMB, and 39 had VWD testing at both time points. Median FVIII and VWF levels were higher during acute bleeding than at follow‐up. The difference in VWF levels between visits was negligible when initial FVIII value was normal. Overall incidence of VWD was 7.5%; 69% of those with VWD had low VWF levels during acute HMB. ConclusionVWD testing during acute HMB detects the majority of individuals with VWD but also leads to elevated levels of VWF, potentially limiting at the accuracy of diagnostic labs during acute bleeding episodes. Delayed testing until resolution of anemia and active bleeding may provide more accurate diagnostic evaluation for VWD.

Increasing levels of von Willebrand factor and factor VIII with age in patients affected by von Willebrand disease

Unlabelled Box AbstractBackgroundIncreasing levels of von Willebrand factor (VWF) and factor VIII (FVIII:C) was associated with age in type 1 von Willebrand disease (VWD). ObjectivesTo evaluate VWF and FVIII:C increase with age in a large group of patients with VWD and low levels of VWF, in whom levels were repeatedly measured. MethodsClinical charts from all patients evaluated at the A. Bianchi Bonomi Center between 1970 and 2018 were reviewed and data on VWF and FVIII:C collected. Patients affected by type 3, severe type 1 and 2N VWD were excluded. The repeated measurements were evaluated by linear mixed‐effects models. A linear association between age and VWF/FVIII:C was shown after the age of 40 years in the linear mixed models and analyzed by calculating the regression slope coefficient (β). ResultsA total of 617 patients were included in the study (314 type 2, 112 type 1, 181 low VWF levels), with a median age at first measurement of 28 years (interquartile range 14/42) and a mean follow‐up of 16 years (standard deviation 11). VWF and FVIII:C increased with age in the whole group. The increase became linear after the age of 40 years (3.68 and 7.44 IU/dL per decade for VWF:activity and FVIII:C). In type 2, FVIII:C increased with age, whereas an increase of both VWF:activity and FVIII:C were shown in patients with type 1 VWD and low levels of VWF. ConclusionsA differential increase of VWF and FVIII:C with age was shown among in different ages and types of VWD.

How we diagnose 2M von Willebrand disease (VWD): Use of a strategic algorithmic approach to distinguish 2M VWD from other VWD types.

von Willebrand disease (VWD) is the most common inherited bleeding disorder and caused by an absence, deficiency or defect in von Willebrand factor (VWF). VWD is currently classified into six different types: 1, 2A, 2B, 2N, 2M, 3. Notably, 2M VWD is more often misdiagnosed as 2A or type 1 VWD than properly identified as 2M VWD. To describe an algorithmic approach to better ensure appropriate identification of 2M VWD, and reduce its misdiagnosis, as supported by sequential laboratory testing. Comparative assessment of types 1, 2A, 2B and 2M VWD using various laboratory tests, including VWF antigen and several VWF activity assays, plus DDAVP challenge data, ristocetin-induced platelet agglutination (RIPA) data, multimer analysis and genetic testing. Types 1, 2A, 2B and 2M VWD give characteristic test patterns that can provisionally classify patients into particular VWD types. Notably, type 1 VWD shows low levels of VWF, but VWF functional concordance (VWF activity/Ag ratios >0.6), with both baseline assessment and post-DDAVP. Types 2A, 2B and 2M VWD show VWF functional discordance (low VWF activity/Ag ratio(s)) dependent on the defect, but type 2M separates from 2A/2B VWD based on specific test patterns, especially with collagen binding vs glycoprotein Ib binding assays. RIPA identifies 2B VWD. Multimers separate 2M from 2A/2B. We provide strategies to improve correct diagnosis of VWD, especially focussed on 2M VWD, and which can be used by most diagnostic haemostasis laboratories, reserving genetic analysis (if required) for confirmation.

ADAMTS13 activity, high VWF and FVIII levels in the pathogenesis of deep vein thrombosis

BackgroundDeep vein thrombosis (DVT) is a common multi-factorial disease with a partially understood aetiology. Although the roles of high factor (F)VIII and von Willebrand factor (VWF) levels are recognized, that of ADAMTS13 is still unclear. AimTo assess the association between ADAMTS13 activity levels, VWF antigen (VWF:Ag) and FVIII coagulant activity (FVIII:C) levels and DVT. Materials and methods365 Italian DVT patients and 292 age- and sex-matched controls were considered. Plasma ADAMTS13 activity was measured using FRETS-VWF73 assay. VWF:Ag and FVIII:C were measured using immunoassay and one-stage clotting assay (ACL TOP analyzer), respectively. Quartile analyses were performed to evaluate the individual association between ADAMTS13 activity, VWF:Ag, FVIII:C and DVT. The combined effect of high VWF levels (> 4th quartile) and low ADAMTS13 levels (< 1st quartile) was evaluated using binary variables. All models were age- and sex-adjusted. Estimated risks were reported as Odds ratio (OR) with 95% confidence intervals (CI). ResultsADAMTS13 activity was lower in DVT patients (94% vs. 98% of controls). Patients with an ADAMTS13 activity <1st quartile (86%) showed a 1.6-fold increased risk of DVT (95%CI, 1.05–2.55). The combination of low ADAMTS13 activity and high VWF:Ag levels was associated with a 15–fold increased risk (95%CI, 7.80–33.80). VWF:Ag and FVIII:C were associated to DVT with a dose-response relationship. ConclusionsADAMTS13 activity < 86% was associated with a moderate risk of DVT. The co-presence of low ADAMTS13 activity and high VWF levels resulted in a strong synergistic effect on DVT risk. The association of VWF:Ag and FVIII:C with DVT was confirmed.

Iron Deficient Anemia May Obscure a Diagnosis of Low VWF, VWD or Mild Hemophilia a in Biological Females with Heavy Menstrual Bleeding

INTRODUCTION Heavy menstrual bleeding (HMB) is one of the most common disease manifestations of biological females with inherited bleeding disorders and is often accompanied by iron deficient anemia (IDA). The most common bleeding disorders identified in biological females are von Willebrand Disease (VWD)/low von Willebrand Factor levels (low VWF) and heterozygosity for factor VIII genetic defects. Several pre-analytical variables including elevated adrenergic stress and estrogen-states can make it challenging to accurately diagnose these conditions as these variables are known to influence VWF and factor VIII activity levels. We sought to investigate whether an iron depleted state impacts the results of a laboratory assessment for VWD/low VWF or mild hemophilia A. METHODS Subjects were recruited from the Spots and Dots clinic (female-identifying bleeding disorder clinic) through the University of Colorado's Hemophilia and Thrombosis Center. Eligible subjects included biological females of any age who had at least two sets of laboratory assessments for von Willebrand levels (VWF antigen, VWF activity, and factor VIII activity level) and markers for total body iron stores (complete blood count and ferritin). Age at time of first testing, iron prescriptions, and underlying bleeding disorder diagnoses were also recorded. IDA was defined as a ferritin less than 20ng/mL with accompanying anemia (Hb &amp;lt;14.3 g/dL). Descriptive statistics and Fisher's exact tests were used to evaluate the association of factor VIII/VWF activity levels and iron stores. RESULTS Thirty-seven subjects were included in the final analysis. The average age at time of first testing was 21.5 years (range 9-50 years). IDA was present in 22 patients at the time of first assessment and in 20 patients at follow up. Serum ferritin improved overall in 23 patients between assessments. Oral iron was prescribed in 20 patients and intravenous iron was prescribed in three. An improvement in serum ferritin predicted a decrease in factor VIII activity (p = 0.0092) on follow-up assessment but did not predict a significant decrease in VWF activity levels (p = 0.0819) (Figure 1). Retesting factor VIII and VWF activity levels after iron repletion led to a diagnosis of low VWF in 4 cases (10.8%) and VWD in 2 cases (5.4%) that would have otherwise been classified as normal without retesting. CONCLUSIONS IDA is frequent in women with HMB and may be insufficiently managed with oral iron therapy in adolescents and those with an underlying bleeding disorder. The fact that many patients remained iron deficient at the time of follow up testing may have blunted the results of this analysis. Despite this limitation, this study still suggests that iron deficient anemia may be a significant enough biological stressor to increase factor VIII and possibly VWF activity levels to a point that may obscure an underlying diagnosis of VWD, low VWF, or hemophilia A. Further investigations are warranted to confirm if universal retesting of VWF and factor VIII activity levels are diagnostically imperative after correction of IDA. Such a recommendation may have a significant impact on this patient population as discovery of an underlying bleeding disorder diagnosis can not only provide an explanation for a patient's HMB but also can identifying individuals who may be at increased risk for bleeding at other sites or during invasive procedures. Disclosures No relevant conflicts of interest to declare.

Platelet Function Analyzer-100 Shows Poor Predictive Value for Children with Low VWF and Mild Platelet Function Defects

Background: The Platelet Function Analyser (PFA)-100 (Siemens) has proven to be a useful screening tool for primary hemostasis. Studies have demonstrated a pooled sensitivity around 90% for all individuals with Von Willebrand Disease (VWD), however the sensitivity for Type 1 is notably poorer than types 2 and 3. Our institution utilizes the PFA-100 as part of a panel of laboratory studies called the "bleeding screen"; this panel is often used as first line screening for inherited bleeding disorders across the hospital system. As the relative frequency of Type 1 VWD and low VWF (defined as Von Willebrand factor (VWF) levels 30-50%) greatly exceed the frequency of individuals with Type 2 and Type 3, when used as a general screen, the PFA-100 likely has reduced sensitivity than documented in the literature. Methods: To evaluate the utility of the PFA-100 as a screening test for VWD and platelet function defects, we retrospectively examined the ordering practices of PFA-100 in relation to the Von Willebrand panel (VWF:antigen, VWF:ristocetin cofactor, Factor VIII), platelet aggregation studies and platelet electron microscopy. We compared results of the testing with diagnostic codes to characterize the test characteristics of the PFA-100 for the diagnosis of VWD or platelet function defects in a pediatric population. We included all patients tested with the PFA-100 from 2017 to 2018 at any Children's Healthcare of Atlanta facility. Exclusion criteria include age under 30 months (reference range established for those over 30 months), hematocrit &amp;lt;35% or platelets &amp;lt;150,000/uL at time of testing due to impact on PFA-100 results. Demographics, laboratory results, bleeding symptoms and diagnoses were collected via chart review. Bleeding disorders were determined by ICD-9 and ICD-10 codes and confirmed via chart review. Descriptive statistics were calculated with frequency and median (interquartile range); comparative statistics calculated with t-tests, chi-square, Fisher's Exact, Mann-Whitney and Spearman rank tests. Test characteristics for PFA-100 and VWD were determined by correlation between PFA-100 and VWD studies sent concurrently; a ristocetin co-factor &amp;lt;50% was considered positive for VWD in the comparative analysis. Test characteristics determined for platelet function testing were dependent on results of platelet aggregation studies and/or platelet electron microscopy. Results: There were 609 children who met inclusion criteria. Median age was 12.2 years (7.3-15.6). The majority were female (62.4%), white (58.5%) and non-Hispanic (77.0%). The most common reason for testing was epistaxis (28.1%), followed by heavy menstrual bleeding (24.8%) and bruising (18.4%). Almost 30% had no bleeding symptoms documented. The majority of individuals also had a VWD profile sent (91.5%), with 418 having the PFA-100 and VWD Profile sent concurrently. The majority of PFA-100 tests were normal (70.6%). Only 91 (14.9%) had additional platelet evaluation with platelet aggregation studies or electron microscopy. Overall, 170 individuals (27.9%) were found to have a bleeding disorder. VWD was diagnosed in 146 individuals (24.0%), a platelet function defect 14 (2.3%) and 11 individuals had other diagnoses including Factor VII deficiency, Hemophilia A and Hemophilia B. The sensitivity of the PFA-100 for VWD was 60.4% (95%CI 46.9-73.6%) and the sensitivity was 60.0% (26.2-87.4%) for platelet function defects. For those with an abnormal PFA, the results of a VWD profile did not determine the likelihood of a provider sending additional testing with platelet aggregation studies or platelet microscopy. Of the 104 individuals with an abnormal PFA and normal VWD studies, only 31 had platelet aggregation testing. There were no differences in demographics or reported symptoms between the two groups. With normal VWD studies, individuals with an abnormal PFA were about 3 times more likely to have platelet aggregation studies sent (p&amp;lt;0.0001). Conclusion: The PFA-100 has poor sensitivity for VWD and mild platelet function defects in pediatric patients. Most individuals screened with a PFA-100 also had a complete VWD panel sent concurrently indicating that this is used as a screen for platelet function defects in our hospital. Given the poor sensitivity for platelet function defects, advanced platelet function testing should be sent based on clinical concern regardless of PFA-100 results when VWD testing is normal. Disclosures Brown: National Hemophilia Foundation, Takeda Clinical Fellowship: Research Funding. Woods:Takeda: Membership on an entity's Board of Directors or advisory committees.