Ristocetin Cofactor Research Articles

A Closer Look at the Newer GP1bM Assay Sheds Light on Unusual Findings

Abstract Von Willibrand disease (VWD) is the most common inherited bleeding disorder. The 2021 Guidelines on VWD diagnosis recommend newer assays measuring the platelet-binding activity of von Willebrand factor (VWF), such as VWF: GPIbM and VWF: GPIbR, over the traditional ristocetin cofactor assay (VWF: RCo). Among these newer assays, the GP1bM INNOVANCE VWF Ac assay obtained de novo FDA approval in October 2022. Its ristocetin-independent activity distinguishes it from other assays. Our laboratory conducted a comprehensive validation on the Stago StaR-Max platform, utilizing Siemens Standard Plasma for calibration. The VWF activity measured by the GP1bM assay was compared with the existing VWF: Ab assay (IL, HemosIL® von Willebrand Factor Activity). The validation studies revealed a good correlation between the two assays. Since implementing the GP1bM assay in October 2023, our attention has been drawn to at least four cases exhibiting unexpectedly high activity levels compared to VWF antigen levels. On average, the activity-to-antigen ratio was 1.9. Notably, all these cases showed the presence of all multimers (low, intermediate, and high). Despite extensive investigation, encompassing considerations like heterophile antibody interference using scantibodies, retesting with different lot numbers of Innovance VWF Ac reagent, and rerunning tests at an outside laboratory, the cause of this anomaly remains elusive. A notable variable lies in the platform disparity between Siemens and Stago. Given the recent introduction of this assay, it has yet to gain widespread adoption in laboratories, resulting in a limited understanding of its practical variations. While recent studies affirm the overall superior performance of newer assays compared to the ristocetin cofactor assay, intricate details of each assay remain less explored. The novelty of the GP1bM assay and its limited usage in laboratories underscore the potential emergence of stable outliers as it becomes more widely adopted. The peculiar cases in our study pose an enigma as to why the reported activity is approximately double the antigen level. As laboratories increasingly embrace and integrate the GP1bM assay, a more complete understanding of its potential variations is expected to unfold. This may elucidate the mysteries surrounding these peculiar cases and ensure the assay’s robust interpretation in clinical settings.

Activity Assessment of Factor Replacement Therapies to Guide Infusion Rate Protocols in Patients with Bleeding Disorders

Abstract Introduction The development of institutional protocols guiding administration of clotting factor replacements in patients with bleeding disorders requires an understanding of product stability over infusion duration. Inclusion of new factor products on formulary at our institution raised consideration for optimal administration routes, including whether a bolus intravenous push versus infusion over 4-12h provided acceptable factor activities. Here we assessed the activity of two clotting factor replacement therapies over a 24h period to guide clinical care protocols. Method This study was performed in the Special Coagulation Lab as a collaboration between pharmacy, hematology, and laboratory medicine. Two vials each of Novoeight, a recombinant antihemophilic factor used in patients with factor VIII deficiency, and Vonvendi, a recombinant von Willebrand Factor (VWF) replacement approved for prophylaxis in adults with Type 3 von Willebrand Disease, were reconstituted to clinically relevant potencies (13 IU/ml, Novoeight; 27 IU/ml, Vonvendi). Products were spiked separately into factor VIII-deficient plasma (Novoeight) or assay diluent (Vonvendi), given inability to obtain VWF-deficient plasma, and tested for activity at various timepoints. Novoeight samples were assessed by traditional one-stage FVIII assays, while Vonvendi samples were assessed for VWF antigen, ristocetin cofactor activity (RCA), and glycoprotein Ib binding activity (GP1bM). Results Novoeight samples maintained similar FVIII activities at all timepoints tested, with differences falling within the coefficient of variation of the assay. Specifically, the two samples had FVIII levels of 108% and 95% at baseline and levels of 98% and 91%, respectively, at 12h, which was the timepoint of greatest interest given plans to allow 12h infusion rates. For Vonvendi samples, measurement of VWF antigen remained fairly stable throughout the 24h period. However, VWF activity decreased in both RCA and GP1bM assays over time, including by 4h. RCA values were 193% and 190% at baseline, 113% and 95% at 4h, and 63% and 63% at 12h. GP1bM was 140% and 133% at baseline, 92% and 91% at 4h, and 56% and 70% at 12h. Together, these results supported implementation of protocols allowing for extended (up to 12h) infusion of Novoeight and short (3-5min) bolus infusion of Vonvendi. Conclusion Our study demonstrated maintained Novoeight activity over the study period, confirming infusion rates of 12h should be efficacious. Conversely, Vonvendi yielded significantly decreased activity levels in as little as 4h, indicating the need for faster infusion rates. Based on our results, current practices at our institution were adapted to include extended infusion for Novoeight only. Drug activity studies may not directly reflect patient outcomes, and additional studies of factor activities following product infusion into patients and clinical hemostasis correlates are necessary. Nevertheless, the clinical lab should continue to play a primary role in testing, monitoring, and developing patient care protocols for therapeutic drugs through multidisciplinary collaboration.

An Automated pre-Dilution Setup for Von Willebrand Factor Activity Assays.

Accurate quantification of von Willebrand factor ristocetin cofactor activity (VWF:RCo) is critical for the diagnosis and classification of von Willebrand disease, the most common hereditary and acquired bleeding disorder in humans. Moreover, it is important to accurately assess the function of von Willebrand factor (VWF) concentrates within the pharmaceutical industry to provide consistent and high-quality biopharmaceuticals. Although the performance of VWF:RCo assay has been improved by using coagulation analyzers, which are specialized devices for blood and blood plasma samples, scientists still report a high degree of intra- and inter-assay variation in clinical laboratories. Moreover, high, manual sample dilutions are required for VWF:RCo determination of VWF concentrates within the pharmaceutical industry, which are a major source for assay imprecision. For the first time, we present a precise and accurate method to determine VWF:RCo, where all critical pipetting and mixing steps are automated. A pre-dilution setup was established on CyBio FeliX (Analytik-Jena) liquid handling system, and an adapted VWF:RCo method on BCS-XP analyzer (Siemens) is used. The automated pre-dilution method was executed on three different, most frequently used coagulation analyzers and compared to manual pre-dilutions performed by an experienced operator. Comparative sample testing revealed a similar assay precision (coefficient of variation = 5.9% automated, 3.1% manual pre-dilution) and no significant differences between the automated approach and manual dilutions of an expert in this method. While no outliers were generated with the automated procedure, the manual pre-dilution resulted in an error rate of 8.3%. Overall, this operator-independent protocol enables standardization and offers an efficient way of fully automating VWF activity assays, while maintaining the precision and accuracy of an expert analyst. Key features • Automated pre-dilution setup for von Willebrand factor concentrates of various natures. • Combination of a liquid handling system (CyBio FeliX) with a coagulation analyzer (BCS-XP). • Simplifies method transfer to other laboratories. • Basic training for CyBio FeliX and BCS-XP is required. Graphical overview VWF:RCo assay principle and measurement setup. Platelets (yellow ellipsoids) with negative surface charge (- - -) are treated with formaldehyde, which partly denatures the cell surface and thus stabilizes platelets for use as assay reagents. Stabilized platelets (dark-yellow-framed yellow ellipsoids) are then brought in contact with ristocetin A (chemical structure shown; black dots), which binds to the platelet surface and facilitates binding of VWF (green circles). The graphs show an example of quantitative determination of platelet agglutination by measurement of light transmission, where increasing amounts of VWF increase light transmission over time. The photo in the left-bottom corner shows the CyBio FeliX setup for VWF sample dilution and the photo in the right-bottom corner displays the BCS-XP system, which is used for VWF:RCo measurements.

Von Willebrand Factor Collagen-Binding Activity and Von Willebrand Factor-Mediated Platelet Adhesion in Patients with Coronary Artery Disease.

In this study, we investigated von Willebrand factor (VWF)-related parameters in 30 patients with stable coronary artery disease (CAD) and 50 patients without CAD. In both groups, the following were measured: the VWF antigen level (VWF:Ag); the VWF ristocetin cofactor activity (VWF:RCo); the VWF collagen-binding activity (VWF:CB); and VWF-mediated platelet adhesion. Platelet adhesion was measured in whole blood at a shear rate of 1300 s-1 using a microfluidic chamber with a collagen-coated surface. VWF:Ag and VWF:RCo were found to be the same in both groups of patients. However, VWF:CB was found to be lower in patients with CAD compared with patients without CAD, with values of 106.7% (82.1; 131.6) and 160.4% (112.5; 218.1), respectively (p < 0.001). The decrease in platelet adhesion after GPIb inhibition was more pronounced in patients with CAD compared with patients of the control group, with recorded values of 76.0% (60.6; 82.1) and 29.3% (0.0; 60.4), respectively (p < 0.001). After adjusting for traditional risk factors, the odds ratio for CAD was found to be 0.98 (95% CI, 0.97-0.99; p = 0.011) per 1% increase in VWF:CB activity, and 1.06 (95% CI, 1.03-1.09; p < 0.001) per 1% decrease in GPIb-mediated platelet adhesion. The findings presented in this paper indicate a possible critical role played by complex VWF-collagen-platelet interactions in the development of CAD.

Menorrhagia in inherited bleeding disorders in Iraqi women

Abstract: BACKGROUND: Menorrhagia, or excessive menstrual bleeding, is a common symptom in women with inherited bleeding disorders; they are conditions where the blood ability to clot is impaired. Some of the common bleeding disorders include von Willebrand disease (VWD), clotting factor deficiencies, and platelet function disorders. OBJECTIVE: To assess different types of inherited bleeding disorders in women with menorrhagia referred to the National Center of Hematology/Mustansiriyah University in Baghdad/Iraq. PATIENTS AND METHODS: A prospective study was carried out on 193 women who had experienced menorrhagia for a duration of 3 years, from 2020 to 2023. These women sought consultation at the National Centre of Hematology/Mustansiriyah University. All participants were diagnosed through various laboratory tests, including complete blood count, blood film, blood group and Rh, bleeding time, prothrombin time, activated partial thromboplastin time, fibrinogen level, factor assay, von Willebrand factor antigen using ELISA technique, ristocetin cofactor, and platelet function test. RESULTS: Out of the 193 women with menorrhagia who participated in this study, the majority of whom had an unidentified cause (36.3%), followed by VWD (30.1%) and platelet function disorders (21.2%). Other bleeding disorders (thrombocytopenia and factors deficiencies) were 5.7% and 6.7%, respectively. Furthermore, the results showed that there was a significant difference in family history and consanguinity between patients with a hereditary bleeding disorder and nonhereditary bleeding disorder (P &lt; 0.001). CONCLUSIONS: Fifty eight percent of females with Menorrhagia in this study have inherited bleeding disorders(IBDs), VWD, and thrombasthenia account for 51.3% are the most common causes of inherit bleeding disorder (IBD). Consanguineous marriage should be discouraged in Iraqi society to reduce such inherited diseases.

Prevalence and characterization of anti-VWF antibodies in a population of patients with type 3 VWD

Abstractvon Willebrand disease (VWD) is an inherited bleeding disorder caused by quantitative or qualitative defects in the von Willebrand factor (VWF) protein. Type 3 VWD has a severe bleeding phenotype caused by the absence of VWF, in which treatment usually involves replacement therapy with VWF-containing products. The immune system can react to the VWF product and form anti-VWF antibodies to neutralize or clear the VWF, which can compromise efficacy of treatment or lead to anaphylaxis. Current diagnostic testing is limited to the detection of anti-VWF antibodies that neutralize VWF binding to platelets by using a ristocetin cofactor assay. We set out to develop assays to identify both neutralizing and nonneutralizing antibodies to screen, quantify, and characterize anti-VWF antibodies in samples from the Zimmerman Program, a large multicenter study of patients with VWD. We detected anti-VWF immunoglobulin G (IgG) or IgM antibodies in 18% of 49 unrelated individuals with type 3 VWD. The antibodies ranged in concentration and consisted of 33% nonneutralizing and 67% neutralizing to factor VIII, collagen III, platelet glycoprotein Ib alpha (GPIbα), and/or collagen IV binding. Of the positive type 3 VWD samples, 8 of 9 were IgG, which were further subclassified into mostly IgG1 and IgG4 antibodies. Through a series of testing methods, we identified VWF-specific antibodies in 9 unrelated individuals with type 3 VWD with varying demographics, bleeding phenotypes, and genetic variants. This anti-VWF antibody testing strategy provides a useful tool to assess risk and better navigate treatment options for patients with type 3 VWD.

Analytical and Clinical Validation of a Non-Ristocetin Based VWF Assay on 2 Automated Analyzers in a Large Reference Laboratory.

Historically, von Willebrand factor (VWF) activity assays utilized ristocetin despite limitations including poor limits of detection and high imprecision. Newer VWF activity assays such as the INNOVANCE® VWF Ac assay, however, do not rely on ristocetin to measure platelet-dependent VWF function. The purpose of this study was to evaluate the analytical and clinical performance of the Siemens Healthineers INNOVANCE VWF Ac Assay on the Siemens BCS® XP and the Sysmex® CS-2500 systems in a large reference laboratory setting. Performance indicators for the INNOVANCE VWF Ac assay were the limit of quantitation (LoQ), precision, and method comparison. Method comparison studies were performed using remnant plasma patient samples from routine coagulation tests and analyzed using both the INNOVANCE VWF Ac assay and the Siemens Healthineers ristocetin-dependent BC von Willebrand Reagent. Evaluation of the INNOVANCE VWF Ac assay on the BCS® XP and CS-2500 systems demonstrated good precision and a lower LoQ compared to the BC von Willebrand Reagent. Method comparisons support the use of the INNOVANCE VWF Ac assay on the BCS® XP and CS-2500 systems to measure platelet-dependent VWF function. The INNOVANCE VWF Ac assay was able to further assist in von Willebrand disease classification in 6/7 (86%) samples when the result was below the LoQ for the BC von Willebrand Reagent (ristocetin cofactor activity). These data are consistent with the 2021 American Society of Hematology/International Society on Thrombosis and Haemostasis/National Hemophilia Foundation/World Federation of Hemophilia von Willebrand disease guidelines that suggest using newer assays such as the INNOVANCE VWF Ac assay in place of ristocetin cofactor activity assays.

Excessive cleavage of von Willebrand factor multimers by ADAMTS13 may predict the progression of transplant-associated thrombotic microangiopathy

BackgroundTransplant-associated thrombotic microangiopathy (TA-TMA) is a fatal complication of hematopoietic stem cell transplantation and is characterized by severe thrombocytopenia, hemolytic anemia, and organ dysfunction. In response to several possible triggers, dynamic multimetric change in von Willebrand factor (VWF) may contribute to inducing microthrombi in circulation in TA-TMA. ObjectivesBy performing VWF multimer analysis and measuring VWF-degradation product (DP), we unraveled the relationship between multimeric changes in circulating VWF and the pathogenesis of TA-TMA. MethodsThis study analyzed 135 plasma samples from 14 patients who underwent allogeneic hematopoietic stem cell transplantation at a single institute. VWF-associated markers, namely VWF:antigen (VWF:Ag), VWF-DP/VWF:Ag ratio, VWF:ristocetin cofactor activity, VWF:ristocetin cofactor activity/VWF:Ag ratio, and ADAMTS13 activity, were analyzed in these samples collected every 7 days. ResultsThere were 2 patients with definite thrombotic microangiopathy (TMA) and 6 patients who presented with probable TMA that did not progress to definite TMA. Each plasma sample was classified into 3 groups: definite TMA, probable TMA, and non-TMA. VWF multimer analysis showed the absence of high-molecular-weight VWF multimers in probable TMA, whereas the appearance of unusually large VWF multimers was observed in definite TMA. The median value of the VWF-DP/VWF:Ag ratio in probable TMA was elevated to 4.17, suggesting that excessive cleavage of VWF multimers by VWF cleaving enzyme, ADAMTS13, resulted in the loss of high-molecular-weight VWF multimers. ConclusionDuring the transition from probable to definite TMA, drastic VWF multimer changes imply a switch from bleeding to thrombotic tendencies. Extensive VWF-DP and VWF multimer analyses provided novel insights.

ECMO produces very rapid changes in primary hemostasis detected by PFA-200 during lung transplantation: An observational study

BackgroundThe pathology of primary hemostasis is a common complication of extracorporeal membrane oxygenation (ECMO) support. Scientific data describing its changes in patients on short-term ECMO support and the ability and speed of the restoration of its functions are limited. AimsThe aim of this study was to describe the pathology of primary hemostasis induced by short-term ECMO support and its development over time using PFA-200®, ROTEM® platelet and von Willebrand factor (vWF) analyses. MethodsIn patients undergoing lung transplantation surgery using intra-operative veno-arterial ECMO support, blood samples were analyzed using the following tests: PFA-200®, ROTEM® platelet tests, vWF antigen, ristocetin cofactor (RCo) and collagen binding protein (CB) before, during and after ECMO support. ResultsBlood samples from 32 patients were analyzed. All three PFA-200® tests (COL/EPI, COL/ADP and COL/P2Y) showed significant deterioration during ECMO support with rapid restoration after ECMO cessation (p<0.05), suggesting an ECMO-induced primary hemostasis disorder. A significant increase of vWF antigen after ECMO cessation (p<0.05) was found with an increase of ristocetin cofactor and collagen binding protein levels, although it was not significant (p>0.05). ConclusionsShort-term ECMO support induces primary hemostasis pathology. It occurs immediately after initiation but is rapidly restored after ECMO cessation, which is detectable by PFA-200®. Despite there being persistent platelet dysfunction after ECMO cessation as seen with the ROTEM® platelet results, the increased levels of vWF antigen might explain the normal results of primary hemostasis detected by PFA-200®.

Hemoglobin concentration and body mass index are determinants of plasma von Willebrand factor and factor VIII levels

BackgroundVon Willebrand Disease (VWD) is the most common inherited bleeding disorder. VWD is characterized by an abnormal quantity or quality of von Willebrand Factor (VWF). Anemia is often found at presentation for a bleeding disorder evaluation due to chronic blood loss. Objectives/HypothesisWe hypothesized that anemia is associated with elevations in both VWF and factor VIII (FVIII) over baseline. We also hypothesized that obesity would be associated with increased levels of VWF. MethodsWe conducted a single-center review of the electronic health record for patients that had proximal von Willebrand profiles and Hb data. ResultsWe identified 4552 unique subjects with VWF studies and a CBC within 24 h. We found that decreasing hemoglobin inversely correlated with VWF antigen, VWF ristocetin cofactor activity, and FVIII activity. We also found that obesity and Black race were independently associated with increased VWF antigen, activity, and FVIII activity. Hb, race, and body mass index (BMI) continued to be determinants of VWF and FVIII levels in multivariable analysis. ConclusionOur study demonstrates that anemia, race, and BMI were found to be associated with elevation of VWF antigen, VWF activity, and FVIII levels. As many individuals with anemia present for evaluation for a bleeding disorder, these variables need to be considered. Key points- Anemia was found to be associated with elevation of VWF antigen, VWF activity and FVIII levels.- Testing von Willebrand factor at times of anemia may mask a diagnosis of von Willebrand Disease.

Impact of extracorporeal membrane oxygenation treatments on acquired von Willebrand syndrome in patients with out-of-hospital cardiac arrest: a retrospective observational study

BackgroundVon Willebrand factor (vWF) plays a crucial role in hemostasis, acting as a key factor for platelet adhesion/aggregation and as a transport protein for coagulation factor VIII. vWF is secreted as a giant multimer, and it undergoes shear stress-dependent cleavage by a specific metalloproteinase in plasma. Among vWF multimers, high-molecular-weight (large) multimers are essential for hemostasis. Acquired von Willebrand syndrome, linked to various conditions, is a hemostatic disorder due to reduced vWF activity. Extracorporeal membrane oxygenation (ECMO), utilized recently for out-of-hospital cardiac arrest patients, generates high shear stress inside the pump. This stress may induce a conformational change in vWF, enhancing cleavage by a specific metalloproteinase and thereby reducing vWF activity. However, no study has investigated the effects of ECMO on vWF-related factors in patients receiving or not receiving ECMO. This study aimed to elucidate the relationship between ECMO treatment and acquired von Willebrand syndrome-related factors in patients with out-of-hospital cardiac arrest.MethodsThis study included patients with cardiogenic out-of-hospital cardiac arrest admitted to our hospital. The patients were categorized into two groups (ECMO and non-ECMO) based on the presence or absence of ECMO treatment. Plasma samples were collected from patients admitted to the emergency department (days 0–4). The vWF antigen (vWF: Ag), vWF ristocetin cofactor activity (vWF: RCo), and factor VIII activity were measured. Additionally, a large multimer of vWF was evaluated through vWF multimer analysis, utilizing western blotting to probe vWF under non-reducing conditions.ResultsThe ECMO and non-ECMO groups included 10 and 22 patients, respectively. The median ECMO treatment in the ECMO group was 64.6 h. No differences in vWF: Ag or factor VIII activity were observed between the two groups during the observation period. However, the ECMO group exhibited a decrease in large vWF multimers and vWF: RCo during ECMO. Strong correlations were observed between vWF: RCo and vWF: Ag in both groups, although the relationships were significantly different between the two groups.ConclusionsECMO treatment in patients with out-of-hospital cardiac arrest resulted in the loss of large vWF multimers and decreased vWF activity. Hence, decreased vWF activity should be considered as a cause of bleeding during ECMO management.

Rare bleeding disorders in Egyptian females presented with heavy menstrual bleeding: single-center study

BackgroundHeavy menstrual bleeding is an important health problem in women of reproductive age and is also one of the most common symptoms in women with bleeding disorders. Data about the frequency of rare bleeding disorders are limited, and population-based studies are lacking, so we aimed to determine the frequency of rare bleeding disorders among women presented with heavy menstrual periods that cannot be attributed to obvious problems.MethodsComplete blood count and bleeding profiles include activated partial thromboplastin time, prothrombin time, factor VIII activity assay, ristocetin cofactor activity, von Willebrand antigen assay, platelet aggregation tests and other factor assays in 100 out of 300 females presented with unexplained heavy menstrual period, pictorial bleeding assessment chart (PBAC) > 100 as a screening tool for heavy menstrual periods, and or International Society of Thrombosis and Hemostasis-Bleeding Assessment Tool (ISTH-BAT) > 6.ResultsA total of 300 women with heavy menstrual periods without an obvious explained cause were included in our study. Among them, we found 100 (30%) females with a mean PBAC of 234 ± 147 and mean ISTH-BAT of 9 ± 5 denoting HMB may be due to underlying bleeding disorders. Among them, the most common diagnosis was VWD in 30 (30%). Other disorders were as follows: 28 (28%) cases with clotting factor deficiencies, 24 (24%) cases were found to have platelet dysfunction, and in 18% of our studied cases, we did not find a clear cause of their bleeding disorders (unknown).ConclusionRare bleeding disorders are not uncommon and require comprehensive hemostatic evaluation as well as simple tools like PBAC and ISTH-BAT questionnaires for the identification of females presented with unexplained HMB.

Evaluation of an automated von Willebrand factor glycoprotein IbM activity assay compared with 3 alternative von Willebrand factor activity assays

BackgroundTo overcome deficiencies of the traditional von Willebrand factor (VWF) ristocetin cofactor activity assay (VWF:RCo), several automated assays for VWF platelet-binding activity have been developed. Information on the performance of these assays and their diagnostic utility remains limited. ObjectivesTo validate the VWF:glycoprotein IbM assay INNOVANCE VWF Ac and compare it with an automated VWF:RCo assay as well as with an automated assay and a manual VWF:Ab assay and to generate reference ranges and analyze reproducibility of the VWF:glycoprotein IbM assay. MethodsClinical sites enrolled healthy subjects and patients representing the intended use population; VWF activity assays were performed, and results were analyzed. The performance of the INNOVANCE VWF Ac assay was also compared between the BCS XP System and the CS-2500 and CS-5100 analyzers. ResultsThe INNOVANCE VWF Ac assay correlated well with the VWF:RCo assay and the automated HemosIL VWF:Ab assay, with Pearson coefficients of >.9 and a predicted bias of ≤5.0 IU/dL at VWF levels of 30 IU/dL and ≤5.8 IU/dL at the levels of 50 IU/dL, but correlation and bias were not as good when compared with the REAADS manual VWF:Ab assay. Reference ranges observed for healthy subjects correlated well with previously published findings. Reproducibility of the INNOVANCE VWF Ac assay on the BCS XP System and the CS analyzers was excellent, as was correlation among devices. ConclusionThe characteristics of the INNOVANCE VWF Ac assay regarding comparability with other VWF activity assays, reference ranges, and precision support the use of this assay for evaluation of patients with concern for von Willebrand disease.

Coagulation Profile in Neonates with Congenital Heart Disease: A Pilot Study.

Background and Objectives: congenital heart disease (CHD), cyanotic and, to a lesser degree, acyanotic, often are accompanied by coagulation abnormalities, impacting substantially morbidity and mortality. Until now, no consistent hemostatic patterns have been demonstrated in neonates and children with CHD because they represent a variable and heterogenous population. The aim of the present study is to investigate the hemostatic profile, as well as the role of ADAMTS-13 (a disintegrin and metalloprotease with thrombospondin type-1 motives), the cleaving protein of von Willebrand factor (VWF) in neonates with CHD and compare them to healthy age-matched controls. Materials and Methods: twenty neonates with a mean gestational age of 37.1 ± 2.5 weeks were included in the CHD group, and 18 healthy neonates with a mean gestational age of 38.2 ± 1.5 weeks were in the control group. Results: prothrombin time was significantly prolonged, and accordingly, factor VII (FVII) levels were significantly decreased in the CHD group in comparison to controls. Factor VIII (FVIII), VWF, and ristocetin cofactor activity (Rcof) levels were significantly higher in the study vs. control group. Concentrations of ADAMTS-13 were decreased in the CHD vs. control group, but the difference was not statistically significant. Our results, in combination, indicate a balanced hemostatic mechanism, although with greater variability in neonates with CHD, while developmental aspects of coagulation are evident in the specific patient population. Conclusions: the coagulation profile is moderately impaired early in the course of CHD, though increased thrombogenicity is already present and should not be ignored.

Orthognathic surgery in a patient with von Willebrand disease

Aim: This study aims to report the perioperative management of a patient with von Willebrand disease (vWd) who underwent orthognathic surgery. The report follows the guidelines of the Case Report Guidelines (CARE) and focuses on the steps taken to prevent bleeding during the surgical procedure. Methods: A 39-year-old female patient with skeletal Class III was treated with maxillary advancement and mandibular setback. Despite normal test results for ristocetin cofactor activity, measures were taken to prevent bleeding, including atraumatic surgical techniques, use of antifibrinolytic medication, induced hypotension during anesthesia, and preparation of blood products for transfusion during trans and postoperative periods if needed. In the end, these measures were not required. Results: The patient did not experience any bleeding during the surgical procedure or postoperative period, demonstrating the effectiveness of the measures taken to manage their blood dyscrasia. Two years after the surgery, the patient had satisfactory aesthetic and functional results and no evidence of relapse. Conclusion: Thus, this case report demonstrates that vWd does not prevent largescale oral and maxillofacial surgeries such as orthognathic surgery as long as proper precautions are taken pre-, intraand postoperatively.

The rapid change of shear rate gradient is beneficial to platelet activation

Fluid shear plays a key role in hemostasis and thrombosis, and the purpose of this study was to investigate the effect of shear gradient change rate (SGCR) on platelet reactivity and von Willebrand factor (vWF) activity and its mechanism. In this study, we developed a set of microfluidic chips capable of generating different shear gradients and simulated the shear rate distribution in the flow field by COMSOL Multiphysics software. Molecular markers of platelet activation (P-selectin, activated GPIIb/IIIa, phosphatidylserine exposure, and monocyte-platelet aggregate formation) were analyzed by flow cytometry. Platelet aggregation induced by shear gradient was studied by a microfluidic experimental platform, and plasma vWF ristocetin cofactor (vWF: RCO) activity was investigated by flow cytometry. The expression of p-Akt was studied by Western blotting. The results showed that the faster the SGCR, the higher the expression of platelet p-Akt, and the stronger the platelet reactivity and vWF activity. This indicates that fluid shear stress can activate platelets and vWF in a shear gradient-dependent manner through the PI3K/AKT signal pathway, and the faster the SGCR, the more significant the activation effect.

Hemostatic capability of ultrafiltrated fresh frozen plasma compared to cryoprecipitate

This in vitro study evaluated the potential hemostatic effect of fresh frozen plasma (FFP) ultrafiltration on clotting factors, coagulation parameters, and plasma properties. ABO-specific units of FFP (n = 40) were prepared for the concentrated FFP and cryoprecipitate. Plasma water was removed from FFP by ultrafiltration using a dialyzer with a pump running at a 300 mL/min. The aliquot of each concentrated FFP after 50, 100, 200, and 250 mL of fluid removal were measured the standard coagulation assay, clotting activity, and plasma properties to compare those parameters of cryoprecipitate. Concentrated FFP contained 36.5% of fibrinogen in FFP with a mean concentration of 7.2 g/L, lower than the cryoprecipitate level. The levels of factor VIII (FVIII), von Willebrand factor (VWF):antigen (Ag), and VWF:ristocetin cofactor (RCo) were also lower in concentrated FFP, whereas the levels of factor V, factor IX, factor XIII, antithrombin and albumin was higher in concentrated FFP. Maximum clot firmness (MCF) in thromboelastometry was approximately one-half of that in cryoprecipitate. Although the levels of VWF:Ag, VWF:RCo, and FVIII differed depending on the ABO blood types, fibrinogen levels, and MCF were not significantly different among the ABO blood groups in FFP and concentrated FFP.

Von Willebrand factor Ristocetin co-factor activity to von Willebrand factor antigen level ratio for diagnosis of acquired von Willebrand syndrome caused by aortic stenosis

BackgroundSevere aortic stenosis (AS) causes acquired von Willebrand syndrome by the excessive shear stress–dependent cleavage of high molecular weight multimers of von Willebrand factor (VWF). While the current standard diagnostic method is so-called VWF multimer analysis that is western blotting under nonreducing conditions, it remains unclear whether a ratio of VWF Ristocetin co-factor activity (VWF:RCo) to VWF antigen levels (VWF:Ag) of <0.7, which can be measured with an automated coagulation analyzer in clinical laboratories and is used for the diagnosis of hereditary von Willebrand disease. ObjectivesTo evaluated whether the VWF:RCo/VWF:Ag is useful for the diagnosis of AS-induced acquired von Willebrand syndrome. MethodsVWF:RCo and VWF:Ag were evaluated with the VWF large multimer index as a reference, which represents the percentage of a patient’s VWF high molecular weight multimer ratio to that of standard plasma in the VWF multimer analysis. ResultsWe analyzed 382 patients with AS having transaortic valve maximal pressure gradients of >30 mmHg, 27 patients with peripheral artery disease, and 46 control patients free of cardiovascular disease with osteoarthritis, diabetes, and so on. We assumed a large multimer index of <80% as loss of VWF large multimers since 59.0% of patients with severe AS had the indices of <80%, while no control patients or patients with peripheral artery disease, except for 2 patients, exhibited the indices of <80%. The VWF:RCo/VWF:Ag ratios, measured using an automated blood coagulation analyzer, were correlated with the indices (rs = 0.470, P < .001). When the ratio of <0.7 was used as a cut-off point, the sensitivity and specificity to VWF large multimer indices of <80% were 0.437 and 0.826, respectively. ConclusionVWF:RCo/VWF:Ag ratios of <0.7 may indicate loss of VWF large multimers with high specificity, but low sensitivity. VWF:RCo/VWF:Ag ratios in patients with AS having a ratio of <0.7 may be useful for monitoring the loss of VWF large multimers during their clinical courses.

The common VWF variant p.Y1584C: detailed pathogenic examination of an enigmatic sequence change

BackgroundAs knowledge of the human genome has advanced, so too has the recognition that interpretation of the pathogenic nature of sequence variants can be challenging. The von Willebrand factor (VWF) gene exhibits a significant degree of sequence variability, and the first VWF variant associated with type 1 von Willebrand disease (VWD), c.4751 A>G, p.Y1584C, was described in 2003. However, since that time, the pathogenic nature of this variant has remained unclear, being assigned properties ranging from a risk factor to a pathogenic variant. ObjectivesTo provide additional evaluation on the interpretation of pathogenicity for this common VWF variant. MethodsFifty-eight subjects with only the p.Y1584C variant were recruited from 2 cohort studies (the Zimmerman Program and the Canadian type 1 VWD study). Clinical and laboratory phenotypes were assessed. ResultsThe prevalence of the p.Y1584C variant in our cohorts was 23- to 27-fold higher than that in large normal population databases. Significantly more p.Y1584C subjects had an abnormal bleeding score when compared to Y1584 individuals. In comparison with a group of 35 subjects without the p.Y1584C variant, subjects with the variant had lower mean VWF:antigen and VWF:ristocetin cofactor values and significantly higher VWF propeptide/VWF:antigen ratios suggestive of enhanced clearance. ConclusionCollectively, the results of this analysis suggest that p.Y1584C is likely pathogenic, however, due to influences such as incomplete penetrance, variable expressivity, and other genetic modifiers like ABO blood group, the straightforward assignment of pathogenicity to this variant is inevitably challenging.

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.