Von Willebrand Factor Activity Research Articles

Type 2M VWD Laboratory Defects More Consistent Than Bleeding Symptoms across Family Members

Background Von Willebrand disease (VWD) is an inherited bleeding disorder characterized by a defect or decrease of von Willebrand factor (VWF). Type 2 VWD results from qualitative defects in VWF. Type 2M VWD is defined by defective platelet binding to GPIb and/or collagen. While the inheritance of type 2M VWD is autosomal dominant, the extent of symptoms across family members has not been well characterized. Methods Subjects included index cases with type 2M VWD and all enrolled family members from a large US study of VWD (Zimmerman Program). Index cases were enrolled due to a prior diagnosis of VWD. All available family members were enrolled if willing. VWF testing performed included VWF antigen (VWF:Ag), VWF platelet binding by either VWF ristocetin cofactor activity (VWF:RCo) or VWF:GPIbM, collagen binding with types I, III or IV collagen (VWF:CB1, VWF:CB3, VWF:CB4) and VWF multimer distribution. Bleeding scores were calculated using the ISTH bleeding assessment tool (BAT). DNA sequencing was performed for the full length VWF gene. Statistics were calculated using GraphPad Prism with a p value of <0.05 considered significant. Family members were defined as affected if they had VWF activity levels consistent with type 2M VWD and presence of genetic variant if identified. Results 24 index cases, 51 affected family members and 40 unaffected family members were available for analysis. The mean VWF:RCo/VWF:Ag ratio for index cases was 0.5 and the mean VWF:CB/VWF:Ag ratio was 1.05. The VWF:RCo/VWF:Ag ratio was similar in affected family members (0.44, p=NS) but higher as expected in unaffected members (0.89, p<0.001 for index case vs. unaffected, p<0.001 for affected vs. unaffected). In contrast, there was no difference in VWF:CB/VWF:Ag ratios between index cases and affected family members (0.94, p=NS). Data for VWF:GPIbM, collagens I and IV were available only on index cases, and showed low VWF:GPIbM/VWF:Ag (mean 0.79), higher VWF:CBI/VWF:Ag (mean 1.31) and lower VWF:CBIV/VWF:Ag (mean 0.85). There was a negative correlation between VWF:GPIbM and VWF:CBIV, with subjects having either low VWF:GPIbM and normal VWF:CBIV or low VWF:CBIV and normal VWF:GPIbM. Similar results were seen for VWF:CB1 although only 1 subject was diagnosed with type 2M VWD and low VWF:CB1. Median bleeding scores were highest in index cases (7.5), intermediate in affected family members (3) and normal in unaffected family members (1). There was a significant difference between index cases and affected family members (<0.015), and between index cases and unaffected family members (p<0.001). One subject had a genetic variant in the VWF A3 domain, one in the VWF D3 domain and the remainder of index cases had a defect in the VWF A1 domain. Conclusions These findings suggest that decreases in platelet and collagen binding activity increase bleeding risk in families with type 2M VWD. Index cases had higher bleeding scores as compared to affected family members, suggesting that diagnosis of family members may require more attention. Precise understanding of these defects may assist in better diagnosis and treatment of von Willebrand disease.

Utility of Von Willebrand Testing during Acute Bleeding Episodes

Background: The diagnosis of mild bleeding disorders such as von Willebrand disease (VWD) poses many diagnostic challenges. Several patient-specific factors including physiologic, inflammation, anemia and medications can affect VWD testing and lead to falsely elevated values. Given that the physiologic stress may cause falsely normal levels of VW factor and associated tests, determining the appropriate timing for testing remains an area of debate. Testing is often performed during inpatient or emergency department (ED) visits when patients present for bleeding complaints, although these results may be skewed by stress or illness. Initial normal results may falsely reassure a patient and their health care provider, preventing them obtaining repeat testing or pursuing outpatient hematological evaluation. Further study is needed to determine the reliability of VWD evaluation when obtained during episodes of acute bleeding. Methods: This single-center retrospective cohort study included subjects who were evaluated for acute bleeding complaints in the UPMC Children's Hospital of Pittsburgh ED or inpatient units who had VWD testing sent during that visit over a five-year period. Bleeding complaints included were epistaxis, heavy menstrual bleeding, spontaneous ecchymosis, post-procedural hemorrhage or intracranial hemorrhage. VWD test results including von Willebrand antigen (VWF:Ag), factor VIII (FVIII) and ristocetin co-factor (VWF:RCo) levels obtained at the time of ED or inpatient care were compared with those obtained in outpatient follow-up visits. T-tests and Wilcoxon rank sum tests were used to compare VWD test levels across the two time points. Results: Over a 5-year period, 144 patients had VWD testing completed during ED or inpatient evaluations for acute bleeding complaints. The population was primarily Caucasian (71%) with a median age of 9 years old. Fifty-two percent of the population was male. Epistaxis and post-tonsillectomy/adenoidectomy bleeding were the most common presenting complaints, making up 47 and 22% of the population, respectively. Other presenting bleeding complaints included spontaneous bruising (18%), menorrhagia (6%), post-procedural hemorrhage of a digestive organ (4%), and nontraumatic intracranial hemorrhage (3%). Six subjects (4%) met laboratory criteria for a diagnosis of VWD during an acute bleeding episode. Twenty-four percent of the total population was evaluated subsequently by outpatient hematology, and 23% of patients had repeat VWD testing performed. Median levels of VWD tests obtained at initial presentation were 116% for VWF:Ag, 112% for FVIII, and 85% for VWF:RCo, and were not statistically different from those obtained on repeat testing in outpatient follow up. An additional two patients that were not initially diagnosed with VWD met laboratory criteria for VWD on repeat outpatient testing. Conclusions: Among children presenting for emergency or inpatient care for acute bleeding episodes, VWD testing was unlikely to be diagnostic. Interestingly, our study did not find that median VWF:Ag and FVIII levels were higher during acute bleeding as has been suggested in other studies. A minority of patients who were evaluated in the hospital for acute bleeding were subsequently evaluated by hematology, which may have limited these findings. It is possible that obtaining VWD testing at the time of an acute bleeding episode may provide false reassurance to a patient, thus decreasing hematology referrals and follow up. Based on these results, we recommend that for patients evaluated in the ED with mild mucocutaneous bleeding who warrant a bleeding disorder evaluation, VWD testing be postponed until the patient is seen in steady-state by hematology.

Using Whole Exome Sequencing to Identify the Pathogenic Variant of F7 C.681+1 G>t As a Potential Cause of Severe Bleeding Clinic Presentation in a Newborn Baby

Ching-Tien Peng1, 2, 3 Chien-Yu Lin4 Yin-Ting Chen1 1.Division of Pediatric Hematology & Oncology, China Medical University Children's Hospital, Taichung, 40447, Taiwan 2.Department of Biotechnology, Asia University, Taichung, 40447, Taiwan 3.Divisions of Pediatrics, China Medical University Hsinchu Hospital, Zhubei City, Hsinchu County, 30272, Taiwan. 4.Divisions of Laboratory Medicine, China Medical University Hsinchu Hospital, Zhubei City, Hsinchu County, 30272, Taiwan. Objective: The clinical manifestations of Factor VII deficiency vary, most cases remain asymptomatic or mild, and cases with severe clinical presentation are rarely reported. It is a rare hereditary hemorrhagic disorder passed on through autosomal recessive inheritance. We present a 2-day-old male infant with large cephalohematoma and intracranial hemorrhage, who was diagnosed using whole exome sequencing with Factor VII deficiency. Materials and Methods: Whole exome sequencing and Sanger sequencing were used to verify related variants. Other routine blood coagulation and factor activity tests were conducted by Divisions of Laboratory Medicine, China Medical University Hospital, Taiwan. Results: A 2-day-old male newborn was identified to develop left intracranial hemorrhage with unknown causes. The laboratory coagulation factor test results indicated a prolonged prothrombin time and normal activated partial thromboplastin time. The test results for Fibrinogen (279.9 mg/dL) and Factor activity analysis, included Factor VIII (85.6%), Factor V (49.3%), Factor VII (<1.0%), Factor IX (81.3%), and Factor X (42.7%). The results for VWF activity and antigen are normal. Subsequently, whole exome sequencing was used to conduct genetic tests, which revealed the homozygote mutation at F7 c.681+1 G>T (NM_000131). Further variant tests on the family members suggested that the father, mother, and older sister had heterozygote mutation at the same site. Conclusions: We used next-generation sequencing, which uses array-based sequencing to process reactions in parallel and enables the simultaneous investigation of multiple genes at a manageable cost, to identify the variants. While there is still little research on whether there is a relationship between different gene mutations and clinical presentations. The sequencing results revealed homozygote mutation at F7 c.681+1 G>T (NM_000131). The pathogenicity level was indicated to be "Highly pathogenic" in the ClinVar archive. Studies have reported the association of such mutation with severe hemorrhage disorders. Therefore, the present study offers critical empirical insights in that it applies to clinical practice in a clinical setting and identifies a pathogenic variant. We will present the hypothesis mechanism at the ASH meetings.

Abstract 11879: Von Willebrand Factor Activity and Closure Time With Adenosine Diphosphate During Transcatheter Mitral Valve Repair

Introduction: Residual mitral regurgitation (MR) is associated with worse outcomes after transcatheter edge to edge mitral valve repair (TEER) but is difficult to assess by echocardiography. Shear-stress induced by MR leads to altered Von Willebrand factor activity (vWF:Act), also reflected by increased closure time with adenosine diphosphate (CT-ADP), representing potential ways to screen for residual MR. CT-ADP can be assessed easily during TEER and is known to normalize swiftly after the correction of turbulent flow. Hypothesis: The improvement of CT-ADP is quick enough to allow real-time procedural guidance. Methods: We enrolled 39 patients undergoing TEER. MR severity was assessed by echocardiography during the procedure, 24-hours and 1-month post-TEER. CT-ADP was measured before TEER, 8 minutes after each clip deployment, 1 hour and 24 hours after the procedure. CT-ADP values were related with vWF:Act and MR severity at each time point. Results: Of 39 patients after TEER, 6 (15%) and 8 (21%) patients had residual MR ≥ moderate at 24-hours and 1-month respectively. There was no significant change in CT-ADP values during the procedure. The decrease of CT-ADP was however significant 1-hour post-TEER with stable values at 24-hours (last clip deployment: 136 [110-193]; 1 hour: 99 [82-131] and 24 hours: 95 [82-121] seconds, p&lt;0.001). Concomitant increase in vWF:Act was observed after the procedure (baseline: 1.76 [1.29-2.05]; 1 hour: 1.84 [1.79-1.85] and 24 hours: 2.32 [1.84-2.5] IU/ml, p=0.002). Patients were stratified into 3 groups according to the residual MR grade at 1 month (≤ mild vs. moderate vs. &gt;moderate). CT-ADP was not different among the groups (p=0.74). However, the difference in CT-ADP (1 month vs baseline values) was associated with MR improvement at the same time points (r=0.50; p=0.007). Conclusions: Although CT-ADP decreases after TEER and correlates with vWF:Act and MR improvement at 1 month, this decrease is first observed 1 hour after the procedure and does not seem to be quick enough to provide real-time monitoring of MR severity during TEER.

BLOOD TYPE O IS A RISK FACTOR FOR HYPERFIBRINOLYSIS AND MASSIVE TRANSFUSION AFTER SEVERE INJURY.

Background: Blood type O is the most common blood type and has lower von Willebrand factor (vWF) levels (25%-35% lower than non-O blood types). von Willebrand factor is important for initiating platelet attachment and binding factor VIII. We hypothesized that patients with type O blood are at an increased risk of trauma-induced coagulopathy and bleeding post injury. Study Design: Adult trauma activations with known blood type at a level I trauma center with field systolic blood pressure < 90 mm Hg were studied retrospectively. The relationships of blood group O versus non-O to coagulation assays, massive transfusion (MT), ventilator-free days, and mortality were adjusted for confounders. Hyperfibrinolysis (HF) was defined as thromboelastogram of percent lysis in 30 min > 3%, and fibrinolysis shutdown was defined as percent lysis in 30 min < 0.9%. von Willebrand factor activity was quantified on 212 injured patients using a STAGO apparatus. Results: Overall, 268 patients met criteria. Type O patients were more likely to develop HF than non-type O blood patients (43% vs. 29%, P = 0.06) and had significantly lower vWF activity (222% vs. 249%, P = 0.01). After adjustment for New Injury Severity Score and blunt mechanism, type O had higher odds of HF (odds ratio, 1.94, 95% confidence interval, 1.09-3.47) and increased odds of MT (odds ratio, 3.02; 95% confidence interval, 1.22-7.49). Other outcomes were not significantly affected. Conclusion: Type O patients with hypotension had increased HF and MT post injury, and these were associated with lower vWF activity. These findings have implications for the monitoring of HF in patients receiving type O whole-blood transfusions post injury.

Analytical performance verification protocols and performance specifications of platelet-dependent von Willebrand factor activity testing

Objective: To investigate the analytical performance verification protocols and performance specifications of platelet-dependent von Willebrand factor (VWF) activity testing (VWF:GPIbM) for clinical laboratories. Methods: According to Clinical Laboratory Standards Institute (CLSI) documents and National Health Standard of China, the performance verification of VWF:GPIbM was designed and implemented using Sysmex CS-5100 instrument and its corresponding reagents. (1) Precision verification: Two commercial quality control samples (with normal and low activity levels) and three plasma pools (with activity range from 5.0% to 150.0%) were prepared. Each sample was tested five times daily for five consecutive days. The coefficient of variation (CV) of intra-and inter-run precisions were calculated, and the precision evaluation criterion was set according to package inserts. (2) Trueness verification: The calibrator was diluted to five reference materials with activity values of 5.2%, 31.2%, 62.4%, 104.0% and 138.7%, and each reference material was tested five times daily for five consecutive days. The bias between the measured value and the reference value was calculated, and the trueness evaluation criterion was set according to the total allowable error. (3) Linearity verification: Ten pooled plasmas with theoretical value range from 3.6% to 160.4% were prepared for the linearity verification of two calibration curves set by the manufacturer (i.e. low range and normal range calibration curve). Each pooled plasma was tested three times in a single run. The slope and R2 of linear regression of mean of measured value and theoretical value, as well as bias, were calculated, and the linearity evaluation criterion was set according to National Health Standard of China and package inserts. (4) Limit of quantitation verification: The calibrator was diluted to two reference materials with activity values of 3.3% and 2.7%, and each material was tested twelve times. The limit of quantitation evaluation criterion was set according to CLSI document. Results: The CVs of intra-and inter-run were 1.0%-2.5% and 1.1%-2.6%, respectively. The biases of trueness verification were -0.4%, 1.0%, -2.6%, 0.3% and -2.7%, respectively. The linearity verification results of low range (3.6%-31.8%) and normal range (28.4%-160.4%) showed that the slopes of regression equation were 1.021 7 and 0.996 2, respectively, R2 were 0.993 5 and 0.993 9, respectively, and the biases with 0-1.8% and -10.1%-0 of plasmas met the criterion. The biases ranged from -0.4% to 0.3% of test results in the verification of limit of quantitation met the criterion. Conclusion: The verification results of VWF:GPIbM assay for precision, trueness, linearity and limit of quantification meet the performance requirements indicated in the package inserts and the criteria set in this study, which can be taken as a reference of performance verification for the clinical laboratories.

Von Willebrand Factor Level and Activity in Correlation with D-dimer Level among COVID-19 Patients in Saudi Arabia

BACKGROUND: Thrombosis and acute respiratory failure are among the leading causes of mortality in COVID-19 patients. The von Willebrand factor (VWF) is one of the main components in the blood coagulation system. It has been hypothesized that the increased VWF level results from vascular damage because VWF is stored in endothelial cells. Infection of endothelial cells with SARS-CoV-2 can stimulate the release of VWF. This study aimed to determine the level of VWF activity among the Saudi population affected by COVID-19 and investigate the correlation between VWF level and D-dimer level. MATERIALS AND METHODS: This is an analytical, retrospective, observational study conducted in a single-center tertiary hospital at King Fahad Military Medical Complex (KFMMC). A study sample of 80 hospitalized patients (aged ≥18 years) diagnosed with COVID-19 confirmed by nasopharyngeal SARS-COV was randomly included in this study. Frozen blood samples were used to measure VWF antigen (Ag) level and activity for all patients. Historical data on hemostasis markers such as platelets (PLTS), fibrinogen, and D-dimer were obtained retrospectively, as well as demographic and clinical data. RESULTS: Data of 80 patients were analyzed to assess VWF Ag level and activity in correlation to D-dimer level. The mean age of the patients was 58.3 (standard deviation 16.18), with nearly two-thirds being females (62.6%). The most common comorbidities were arterial hypertension (67.5%), diabetes (56.3%), and dyslipidemia (22.5%). Only 10% of patients were obese. The mean values of were 3.25 for D-dimer, 3.55 for fibrinogen, 226.4 for PLTS, 9.88 for white blood cell, 237.04 for VWF Ag, 253.21 for VWF activity, and 70.45 for C-reactive protein. Pearson's correlation coefficient revealed that the correlation between D-dimer and VWF Ag and D-dimer and VWF activity was statistically insignificant (P &gt; 0.05). Only six patients had overt thrombosis, but this has no significant correlation with VWF Ag, activity, D-dimer, or platelet count. VWF Ag and activity were higher in intensive care unit (ICU) than non-ICU patients. However, it is not significant statistically. VWF Ag and activity were significantly higher in deceased patients than in survivors. CONCLUSIONS: The results of this study showed that there was no significant correlation between VWF Ag and activity with D-dimer among Saudi patients with confirmed COVID-19.

Lower levels of vWF are associated with lower risk of cardiovascular disease

ObjectiveThe current study was undertaken to prospectively explore whether having low levels of von Willebrand factor (vWF) antigen and vWF activity reduce the risk for cardiovascular disease and death. MethodsVWF antigen and vWF activity were measured by enzyme‐linked immunosorbent assay and an immunological‐based assay, respectively, in a subsample of 4857 individuals aged between 35 and 74 years old, enrolled between April 2007 and October 2008 in the population‐based Gutenberg Health Study. VWF antigen and activity below the 20th percentile was set as a measure of “low vWF.” Adjusted robust Poisson regression models were used to analyze the relation between low vWF and the incidence of cardiovascular disease (CVD). Consequent adjusted cox regression models as well as cumulative incidence plots were calculated to explore the relation between all‐cause and cardiovascular mortality and low vWF. ResultsVWF activity levels <20th percentile (i.e., <76.2%) were associated with a decreased relative risk for CVD (RR: 0.59, 95% CI: 0.37–0.95), despite adjusting for age and sex. After adjusting for levels of F‐VIII, the association persisted (RR: 0.60, 95% CI: 0.36–0.99). The cumulative incidence plots demonstrated that vWF antigen <20th percentile significantly correlated with decreased cardiovascular mortality. VWF antigen<20th percentile (i.e., <83%) was significantly associated with lower risk of all‐cause mortality, despite adjusting for clinical factors (RR: 61, 95% CI: 0.41–0.91). ConclusionThe study demonstrated that having low vWF activity levels were associated with a lower risk for CVD. Additionally, it revealed a decreased risk of cardiovascular and all‐cause mortality in individuals with low levels of vWF antigen, shining new light on vWF as a potential target for novel therapies.

Von Willebrand Disease-Specific Aspects in Women.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder, which results from a deficiency or dysfunction of von Willebrand factor (VWF). The major symptoms of patients affected by VWD include mucocutaneous and gastrointestinal bleeding, easy bruising, and prolonged provoked bleeding due to injury or surgery. Although women and men are equally likely to be affected by VWD, women continue to be disproportionately affected by the bleeding challenges. Women with VWD suffer from sex-specific symptoms, such as menorrhagia, and are at higher risk of reproductive problems and recurrent miscarriage. Furthermore, pregnant women with VWD are more likely at higher risk of suffering from primary and secondary peripartal hemorrhage and anemia and the need for transfusions. Despite being affected by gynecologic and obstetrical bleeding, women face multiple barriers in obtaining an accurate diagnosis. This constitutes a problem that needs to be addressed, and early appropriate medical care should be ensured. There are several effective treatment options for women with VWD that can significantly improve their quality of life, including desmopressin, VWF concentrates, hormonal therapy, and antifibrinolytic therapy. During pregnancy, the monitoring of VWF activity levels is essential. The peripartal management depends on the type of VWD and on the measured levels of VWF levels and activity prior to delivery.

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.

AML-226 Impairment of Primary Hemostasis as an Additional Risk Factor of Hemorrhage in Patients With Newly Diagnosed Acute Myeloid Leukemia: Ukrainian Prospective Study

Bleeding events in acute myeloid leukemia (AML) are frequent and life threatening, whereas widely used treatment approaches are not always able to satisfy expected outcomes. The primary endpoints were the qualitative and quantitative functions of plasma von Willebrand factor (vWF), which include measurements of vWF activity (vWF:ristocetin cofactor [vWF:RCo]), vWF level (vWF:antigen [vWF:Ag]), factor VIII coagulation activity regarding vWF (vWF:FVIII), and FVIII activity (FVIII) in AML patients. Forty-two patients with newly diagnosed AML (excluding acute promyelocytic leukemia) were included in the study group. The control group included 20 age-matched and sex-matched healthy individuals. The grade (G) of bleeding events was assessed according to the Modified WHO Bleeding Scale (WHO BS). Hemorrhage (G1-4) occurred in 53.3% of patients in the study group during induction therapy. vWF:Ag below normal ranges had been observed in 19% of patients with AML and was associated with the occurrence of severe hemorrhage compared with the patients who had normal vWF:Ag levels and no bleeding episodes (P=0.012). It is important to mention that vWF:Ag levels (median 134, mean 163±18.25) were elevated in most cases (56%) in the main group and are probably associated with a compensatory mechanism for stopping bleeding compared with the control group. In 23.8% of patients with AML, we observed levels of vWF:RCo below normal ranges. Among them, the most frequent bleeding events were G2 (5/10, 50%) and G4 (3/10, 30%); three of them died during the first course of chemotherapy due to gastrointestinal and CNS bleeding. Therefore, we found a statistically significant association between decreased levels of vWF:RCo below normal ranges and the occurrence of severe bleeding episodes (G2-G4) in patients with AML compared with the group that had normal ranges of vWF:RCo and no bleeding events (G0) (P=0.0001). Furthermore, low vWF:FVIII (P=0.033) and FVIII (P=0.037) levels in patients with AML and bleeding episodes G2-G4 had statistical differences compared to non-hemorrhage patients (G0). According to our study, vWF:RCo, vWF:Ag, and vWF:FVIII were associated with hemorrhage in patients with newly diagnosed AML and could be considered predictive factors of bleeding.

Von Willebrand factor activity levels are influenced by driver mutation status in polycythemia vera and essential thrombocythemia patients with well-controlled platelet counts.

von Willebrand factor ristocetin cofactor (vWF activity) and platelet count (PLT) are negatively correlated in patients with polycythemia vera (PV) and essential thrombocythemia (ET). However, vWF activity does not always normalize upon controlling PLT in those patients. To address this issue, we investigated the correlation between vWF activity and PLT in PV and ET patients. The negative correlation between vWF activity and PLT was stronger in calreticulin mutation-positive (CALR+) ET than in Janus kinase 2 mutation-positive (JAK2+) PV or ET groups. When PLT were maintained at a certain level (<600 × 109 /L), low vWF activity (<50%) was more frequently observed in JAK2+ PV patients than in JAK2+ ET (p=.013) or CALR+ ET (p=.013) groups, and in PV and ET patients with ≥50% JAK2+ allele burden than in those with allele burden <50% (p=.015). High vWF activity (>150%) was more frequent in the JAK2+ ET group than in the CALR+ ET group (p=.005), and often associated with vasomotor symptoms (p=.002). This study suggests that some patients with JAK2+ PV or ET have vWF activity outside the standard range even with well-controlled PLT, and that the measurement of vWF activity is useful for assessing the risk of thrombosis and hemorrhage.

ПРОГНОСТИЧЕСКАЯ ЗНАЧИМОСТЬ КЛИНИКО-ЛАБОРАТОРНЫХ МАРКЕРОВ ПОРАЖЕНИЯ НЕРВНОЙ СИСТЕМЫ, АССОЦИИРОВАННЫХ С БЕРЕМЕННОСТЬЮ

Abstract. Objective: To study, to systematize and to evaluate the prognostic significance of clinical and laboratory markers of nervous system damage associated with pregnancy with and without arterial hypertension (AH) in order to determine the main risk factors for the development of stroke. Materials and methods. Assessment of autonomic dysfunction, neuro-ophthalmological examination, additional research methods: laboratory and instrumental methods, including the study of gene polymorphism, CT, MRI Results. Based on the results of constructing a set of logistic regression models that generalize their results of a high probability detection algorithm, it is shown that in order to identify the final group of high risk of developing ischemic stroke in pregnant women, it is necessary to exclude patients without autonomic dysfunction before pregnancy, and also take into account the risks if they are detected in at least two stages. Factors such as the presence of cephalgic syndrome, autonomic dysfunction before pregnancy, contraception, concomitant pathology of more than 3 nosological units, hypoplasia of cerebral vessels, retinal angiopathy according to neuro-ophthalmological examination, elevated levels of fibrinogen and high activity of von Willebrand factor are common risk factors for the development of cerebrovascular accident ischemic type, regardless of the presence or absence of arterial hypertension.

A case of retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations: Long‐term treatment with repeated courses of immunotherapy

AbstractWe present here the case of a 48‐year‐old man who first developed retinopathy, and motor deficit and aphasia occurred 8 years later. A tumor‐like lesion was seen by brain MRI. He was diagnosed with retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL‐S) because a three prime repair exonuclease 1 (TREX1) gene abnormality was identified. After intravenous methylprednisolone pulse (IVMP) and intravenous immunoglobulin (IVIg) therapy, cerebrospinal fluid (CSF) test results and clinical manifestations improved. However, a new lesion appeared 3 years later. Immunotherapy became ineffective, and repeated relapses occurred. We evaluated the results of laboratory tests and brain MRI for 6 years after the first treatment. Coagulation tests, including measurements of vWF activity, remained high, so immunotherapy was thought to have a limited effect.

Analysis of College of American Pathologists von Willebrand Factor Proficiency Testing Program

Von Willebrand factor (VWF) level and/or function is altered in von Willebrand disease (VWD), the most common heritable bleeding disorder worldwide. Laboratory assessment of VWF is continually evolving. Historically, the primary method for the assessment of VWF platelet-binding activity was the ristocetin cofactor assay (VWF:RCo). Contemporary alternative measures of VWF platelet-binding activity include VWF:GPIbR (recombinant; using ristocetin), VWF:GPIbM (recombinant; gain-of-function mutant), and monoclonal antibody. Recently, the American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia collaboration issued guidelines recommending the use of newer assays of VWF platelet-binding activity (VWF: GPIbM, VWF: GPIbR) over VWF:RCo, given known limitations of the VWF:RCo assay. Despite this recommendation, the newer VWF:GPIbM and VWF:GPIbR assays are not United States Food and Drug Administration cleared, limiting their availability in the United States. We sought to assess assay utilization trends, agreement of VWF testing methods, and imprecision of VWF testing (based on assigned sample type) from the College of American Pathologists Proficiency Testing Surveys. The analysis confirms that, while VWF antigen testing has low imprecision, the various VWF activity assays have significant interassay variability, with VWF:RCo showing greater imprecision than the newer GPIb-binding assays. The overall trends in assay utilization reflect the barriers to complete compliance with modern VWD diagnostic guidelines in North America.

P11.27: Changes in Markers of Coagulation and Fibrinolysis Offer Insights Into Pathophysiological Aspects of Preservation Injury During Normothermic Liver Perfusion

Background: The perfusate used in normothermic machine perfusion (NMP) is mainly composed of red packed blood cells and colloid solution and is therefore free from thrombocytes and coagulation factors. Our aim was to monitor changes in composition of coagulation factors during NMP and to investigate their association with liver function during NMP and after transplantation. Methods: NMP has been performed on a heterogenous study group of 16 grafts that included 12 extended criteria donor livers. Factor V activity (FV), factor XIII activity (FXIII), van Willebrand factor activity (vWF), D-dimer, plasminogen-activator-inhibitor (PAI-1) and thrombocyte count in perfusate were assessed. Liver and bile duct biopsies were taken before and after perfusion and after reperfusion. Median follow-up after transplantation was 11 months (IQR: 6.4-12). Results: NMP and assessment of 16 livers resulted in 10 livers that were successfully transplanted. Main reasons for decline included inability to clear lactate, low bile quality, or signs of fibrosis in the frozen section. Two livers presented with increased D-dimer levels during perfusion (8.7 µg/mL and 12.3 µg/mL vs. mean peak D-dimer of 3.7 µg/mL SD: 3.1). One liver was transplanted, the histological analysis of the bile duct biopsies taken before implantation showed sclerosing cholangitis. Additionally, vWF activity during perfusion of this liver was increased (13 % vs. mean peak vWF activity of 6.4% SD: 2.5). The recipient had to be treated with a stent for an anastomotic stricture. The second liver with elevated D-dimer was severely steatotic and the only liver out of the study group that did not produce bile and was therefore declined for transplantation. The graft additionally presented with high levels of PAI-1 (299 IU/mL vs. mean peak PAI-1 of 186 IU/mL SD: 155) and increased FXIII activity in perfusate (158 % vs. mean peak FXIII activity 45% SD: 49). PAI-1 was also elevated in another three livers during perfusion, of which one was discarded due to increasing lactate after initial clearing and high grade of steatosis (peak PAI-1 605 IU/mL). Both other livers were successfully transplanted, one of the two recipients later developed an anastomotic stricture. Each of the three cases with increased PAI-1 levels coincided with peaks in either thrombocyte count, bilirubin or FV activity. Conclusion: Changes in perfusate composition of coagulation and fibrinolysis factors offer interesting new insights in pathophysiological aspects of preservation injury and might allow for additional graft assessment during longer courses of NMP. Prospective studies are needed to validate these initial findings.

Laboratory Diagnosis of von Willebrand Disease (VWD): Geographical Perspectives.

von Willebrand disease (VWD) is reportedly the most common inherited bleeding disorder, and can also arise as an acquired (von Willebrand) syndrome (AVWS). The hemostasis laboratory plays a key role in the diagnosis or exclusion of VWD/AVWS, which may otherwise be suspected due to the patient's clinical (bleeding) history. VWD/AVWS arise from deficiency and/or defects in the adhesive plasma protein, von Willebrand factor (VWF). VWF undertakes various roles within hemostasis, but principally acts within primary hemostasis to anchor platelets to sites of vascular damage, thereby facilitating thrombus formation to arrest bleeding. The diagnosis or exclusion of VWD/AVWS requires laboratory testing for both VWF level and activity, with the latter potentially comprising several of a potential plethora of different assays. Complete diagnosis of VWD also requires the differentiation of VWD type, with six types comprising the current classification (i.e., qualitative [types 2A, 2B, 2M, 2N VWD] vs. quantitative [types 1 and 3 VWD] deficiency/defects). Although appropriate diagnosis and type classification hold important therapeutic consequences, these remain problematic and sometimes elusive for some laboratories to achieve. This report reviews the laboratory aided diagnosis or exclusion of VWD from a geographic perspective, and focuses on the disparities of approaches and methods in different regions of the world. This is primarily done from the perspective of data available from published reports related to external quality assessment (or proficiency testing) from different geographic localities. Moreover, differences in approaches between laboratories may arise due to differential adherence of particular guidelines, as well as regulatory aspects and predominance of local manufacturers and suppliers.

External Quality Assessment Data for Investigation of von Willebrand Disease: Focus on Relative Utility of Contemporary Functional von Willebrand Factor Assays. The United Kingdom National External Quality Assessment Scheme (UK NEQAS) Experience.

Von Willebrand disease (VWD) is one of the most common hereditary bleeding disorders. Effective management of patients and their families depends on accurate diagnosis and subtype classification, and quality assurance including participation in proficiency testing programs is essential to ensure the accuracy of the panel of assays required to achieve this diagnosis. We report here findings from recent external quality assessment (EQA) exercises, as well as from a questionnaire about diagnostic practices employed by centers in the United Kingdom National Quality Assessment Scheme (UK NEQAS) performing von Willebrand factor (VWF) assays. Plasma samples from donors with VWD, "normal" donors, the International Society for Thrombosis and Haemostasis Scientific Subcommittee (ISTH SSC) plasma standard, and whole blood samples were sent to participants in the UK NEQAS BC program for VWF investigation. Calibration of lot#5 of the ISTH SSC plasma standard was shown to give improved comparability between the recovered value from an EQA exercise and the assigned potency for VWF activity assays. Diagnostic accuracy and precision amongst UK NEQAS participants was good, with an average 99% of centers reporting the correct interpretation for normal, type 1 and type 2 VWD samples, 100% diagnostic accuracy for centers performing FVIII binding assays, and good agreement amongst centers performing multimeric analysis. Genetic analysis of the VWF gene by specialist centers demonstrated errors in the genotyping process in one center, but also demonstrated failings in the interpretation of results in other centers. Despite evidence of good laboratory accuracy and precision in their assays, a questionnaire identified marked variation in diagnostic criteria employed, underlining the importance of guidelines to support the diagnosis of VWD.

Analysis of College of American Pathologists von Willebrand Factor Proficiency Testing Program.

Von Willebrand factor (VWF) level and/or function is altered in von Willebrand disease (VWD), the most common heritable bleeding disorder worldwide. Laboratory assessment of VWF is continually evolving. Historically, the primary method for the assessment of VWF platelet-binding activity was the ristocetin cofactor assay (VWF:RCo). Contemporary alternative measures of VWF platelet-binding activity include VWF:GPIbR (recombinant; using ristocetin), VWF:GPIbM (recombinant; gain-of-function mutant), and monoclonal antibody. Recently, the American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia collaboration issued guidelines recommending the use of newer assays of VWF platelet-binding activity (VWF: GPIbM, VWF: GPIbR) over VWF:RCo, given known limitations of the VWF:RCo assay. Despite this recommendation, the newer VWF:GPIbM and VWF:GPIbR assays are not United States Food and Drug Administration cleared, limiting their availability in the United States. We sought to assess assay utilization trends, agreement of VWF testing methods, and imprecision of VWF testing (based on assigned sample type) from the College of American Pathologists Proficiency Testing Surveys. The analysis confirms that, while VWF antigen testing has low imprecision, the various VWF activity assays have significant interassay variability, with VWF:RCo showing greater imprecision than the newer GPIb-binding assays. The overall trends in assay utilization reflect the barriers to complete compliance with modern VWD diagnostic guidelines in North America.

Analysis of College of American Pathologists von Willebrand Factor Proficiency Testing Program

Von Willebrand factor (VWF) level and/or function is altered in von Willebrand disease (VWD), the most common heritable bleeding disorder worldwide. Laboratory assessment of VWF is continually evolving. Historically, the primary method for the assessment of VWF platelet-binding activity was the ristocetin cofactor assay (VWF:RCo). Contemporary alternative measures of VWF platelet-binding activity include VWF:GPIbR (recombinant; using ristocetin), VWF:GPIbM (recombinant; gain-of-function mutant), and monoclonal antibody. Recently, the American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia collaboration issued guidelines recommending the use of newer assays of VWF platelet-binding activity (VWF: GPIbM, VWF: GPIbR) over VWF:RCo, given known limitations of the VWF:RCo assay. Despite this recommendation, the newer VWF:GPIbM and VWF:GPIbR assays are not United States Food and Drug Administration cleared, limiting their availability in the United States. We sought to assess assay utilization trends, agreement of VWF testing methods, and imprecision of VWF testing (based on assigned sample type) from the College of American Pathologists Proficiency Testing Surveys. The analysis confirms that, while VWF antigen testing has low imprecision, the various VWF activity assays have significant interassay variability, with VWF:RCo showing greater imprecision than the newer GPIb-binding assays. The overall trends in assay utilization reflect the barriers to complete compliance with modern VWD diagnostic guidelines in North America.