Von Willebrand Disease Screening Research Articles

Epidemiological, Demographic, and Clinical Characteristics of Von Willebrand Disease Patients in Zahedan City, Iran: A Descriptive Study

Background: Von Willebrand disease (VWD) is one of the most common coagulative diseases, so identifying the effective factors in preventing this complication is essential. The study aimed to evaluate the frequency of demographic and epidemiological findings in VWD patients referred to a hospital in Zahedan, Iran. Materials and Methods: This study was performed on 76 patients with VWD referred to Hazrat Ali-Asghar Hospital in Zahedan City, Sistan, and Baluchestan province. After obtaining consent from the patients, the demographic information and clinical symptoms of the disease were recorded. All statistical analyses were performed using SPSS 22.0 software. All descriptive data were expressed as mean ±SD and percent (%) depending on the continuous and dichotomous variables. A P-value ≤0.05 was considered significant statistically. Results: The present study results showed that the highest age group of VWD patients at the time of disease diagnosis was in the age group 1-5 years (47.3%), and most patients had type III VWD (80.3%). It was also found that 67.1% of patients had a positive family history and their parents' consanguineous marriage (77.6%). The most common complaints were epistaxis (88.15%), cutaneous bleeding (78.94%), and oral cavity bleeding (61.84%), respectively. Conclusion: Due to the high prevalence of VWD in consanguineous marriages and an increase in adverse complications and symptoms in VWD patients, proper diagnosis and screening at an early age, especially in people with family history, is essential. Efforts are needed to develop national registries and widely provide the required and available basic services for diagnosis and treatment.

Разработка метода первичного скрининга болезни Виллебранда на основе балльной оценки выраженности геморрагических проявлений по результатам опроса пациентов

Разработка метода первичного скрининга болезни Виллебранда на основе балльной оценки выраженности геморрагических проявлений по результатам опроса пациентов

Von Willebrand factor unfolding mediates platelet deposition in a model of high-shear thrombosis

Thrombosis under high-shear conditions is mediated by the mechanosensitive blood glycoprotein von Willebrand factor (vWF). vWF unfolds in response to strong flow gradients and facilitates rapid recruitment of platelets in flowing blood. While the thrombogenic effect of vWF is well recognized, its conformational response in complex flows has largely been omitted from numerical models of thrombosis. We recently presented a continuum model for the unfolding of vWF, where we represented vWF transport and its flow-induced conformational change using convection-diffusion-reaction equations. Here, we incorporate the vWF component into our multi-constituent model of thrombosis, where the local concentration of stretched vWF amplifies the deposition rate of free-flowing platelets and reduces the shear cleaning of deposited platelets. We validate the model using three benchmarks: in vitro model of atherothrombosis, a stagnation point flow, and the PFA-100, a clinical blood test commonly used for screening for von Willebrand disease (vWD). The simulations reproduced the key aspects of vWF-mediated thrombosis observed in these experiments, such as the thrombus location, thrombus growth dynamics, and the effect of blocking platelet-vWF interactions. The PFA-100 simulations closely matched the reported occlusion times for normal blood and several hemostatic deficiencies, namely, thrombocytopenia, vWD type 1, and vWD type 3. Overall, this multi-constituent model of thrombosis enables macro-scale 3D simulations of thrombus formation in complex geometries over a wide range of shear rates and accounts for qualitative and quantitative hemostatic deficiencies in patient blood.

051 Heavy menstrual bleeding in teenagers: Haematological issues

Up to one in three adolescent girls who present to the gynecologist with heavy menstrual bleeding (HMB) may have an underlying bleeding disorder [ [1] Zia A. Jain S. Kouides P. Zhang S. Gao A. Salas N. et al. Bleeding disorders in adolescents with heavy menstrual bleeding in a multicenter prospective US cohort. Haematologica. 2020; 105: 1969-1976 Crossref PubMed Scopus (18) Google Scholar ]. Unfortunately, this often remains unrecognized evidenced by an average diagnostic delay of 14–16 years for women who are diagnosed with a congenital bleeding disorder [ 2 Kirtava A. Crudder S. Dilley A. Lally C. Evatt B. Trends in clinical management of women with von Willebrand disease: a survey of 75 women enrolled in haemophilia treatment centers in the United States. Haemophilia. 2004; 10: 158-161 Crossref PubMed Scopus (91) Google Scholar , 3 Atiq F. et al. Major differences in clinical presentation, diagnosis and management of men and women with autosomal inherited bleeding disorders. EClinicalMedicine. 2021; 32: 100726 Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar ]. Even in the high resource setting, screening rates for von Willebrand disease, the most common inherited bleeding disorder, are strikingly low, despite ACOG recommendations [ [4] Jacobson A.E. Vesely S.K. Brien S.H.O. Campbell J. Patterns of von Willebrand disease screening in girls and adolescents with heavy menstrual bleeding. Obstet Gynecol. 2018; 131: 1121-1129 Crossref PubMed Scopus (15) Google Scholar ]. Missed diagnosis may lead to social impairment, psychological and physical problems caused by inadequate treatment and subsequent complications.

Screening for von Willebrand disease does not impact posttonsillectomy bleeding in a low-risk population.

Bleeding is an important complication in children following tonsillectomy. Screening with coagulation tests prior to procedure is common to assess bleeding risk in the perioperative period, although ASH/ASPHO Choosing Wisely guidelines recommend against routine PT/PTT testing. Our aim was to compare von Willebrand factor antigen (VWF:Ag) and activity levels among patients with postoperative bleeding following tonsillectomy to evaluate for potential risk for bleeding. Eligible subjects were aged 0-18 without significant personal or family history of major bleeding. Postoperative bleeding diaries were collected and symptoms measured using a postoperative bleeding score. Plasma VWF levels were drawn at time of anesthesia administration. Postoperative bleeding occurred in 248 cases out of 1399 total subjects. Median VWF:Ag was 86 in patients with postoperative bleeding scores of 1-2, 86 for scores 3-4, 84 for scores 5-6, and 83 for scores >6, with no significant difference among groups (p=.98). Additionally, no difference was observed for subjects with multiple days of postoperative bleeding as compared to those with only 1day of postoperative bleeding. Finally, no difference in VWF:Ag was observed for subjects whose first reported bleed occurred early in the postoperative course compared to those whose first reported bleed occurred later. VWF:Ag does not correlate with severity of bleeding, time of onset of first bleeding event, or recurrence of bleeding in healthy children with no personal or family history of bleeding who have postoperative bleeding following tonsillectomy. This data does not support routine von Willebrand disease screening prior to tonsillectomy.

A Comparative Evaluation of an Automated Functional Assay for Von Willebrand Factor Activity in Type 1 Von Willebrand Disease.

Backgroundvon Willebrand factor ristocetin cofactor activity (VWF:RCo) is the standard functional assay used for von Willebrand disease (VWD) diagnosis. However, it has some drawbacks including being time consuming and labor intensive and having high inter-laboratory variability. The HemosIL VWF activity assay has the advantages of both high speed and automation. The purpose of this study was to prospectively compare these two functional assays for type 1 VWD detection.MethodsPlasma samples from 108 subjects were assessed in this study. HemosIL VWF activity was measured with the HemosIL latex immunoturbidimetric commercial kits by the ACL TOP coagulation analyzer. VWF:RCo was measured by platelet aggregation method. Pearson correlation analyses were performed to estimate the correlation of HemosIL VWF activity with VWF:RCo. Receiver-operator characteristic (ROC) curve analysis was used to evaluate the performance of the two diagnostic tests.ResultsThe correlation coefficient between VWF:RCo and HemosIL VWF activity was 0.874 overall and was 0.761 and 0.811 in the cohorts of type 1 VWD and non-VWD, respectively. The sensitivity and specificity of HemosIL VWF activity assay for type 1 VWD identification were 94.7% and 80.0%, respectively, and the ROC curve of HemosIL VWF activity was larger than that of VWF:RCo (0.928 vs 0.863, p=0.0138). Finally, the positive and negative predictive values of the HemosIL VWF activity assay for type 1 VWD detection were 72.0% and 96.6%, respectively.ConclusionOur results demonstrate that the HemosIL VWF activity assay was an effective method for type 1 VWD screening and diagnosis. It carried good sensitivity and specificity and had a higher ROC curve than VWF:RCo besides showing good correlation with VWF:RCo. With its advantages of greater speed and automated performance, these results suggest that the HemosIL VWF activity assay was reliable and precise in the clinical setting.

Diagnosis of von Willebrand disease: An assessment of the quality of testing in North American laboratories

Laboratory diagnosis of von Willebrand Disease (VWD) is complex. Reliance on laboratory testing can be problematic as different VWD screening panels, assays and methodologies can produce analytic variability in test results. To compare the degree of imprecision among the VWD assays and within the platelet binding activity (PBA) assays, to determine the consensus among the VWD assays for correct classification of sample results, and to determine consensus among laboratories' von Willebrand factor (VWF) multimer interpretations and final interpretations of the VWD panels. Proficiency testing results from the North American Specialized Coagulation Laboratory Association (NASCOLA) submitted by laboratories from 2010 to 2019 for all normal, type (T) 1 VWD and T2 VWD samples were analysed. Imprecision was lowest for VWF antigen and highest for collagen binding activity (CBA) with median coefficient of variation (CV) of 12% (interquartile range (IQR) 7%) and 23% (IQR 21%) respectively. Within the VWF PBA assays, the gain-of-function mutant GP1b binding (VWF: GP1bM) methods had the least imprecision (CV 9%, IQR 10%). All assays, including the various PBA methods had excellent consensus. The majority of laboratories agreed that normal (median consensus-82%, IQR 16%) and T1 VWD (median consensus-100%, IQR 9%) samples had normal multimer distribution. Consensus among laboratories for final interpretations was excellent for normal samples (median 81%, IQR 8%), good for T1 VWD samples (median 59%, IQR 9%), and fair for T2 VWD samples (median 44%, IQR 21%). Consensus on final interpretation decreased as sample complexity increased.

A Continuum Model for the Unfolding of von Willebrand Factor.

von Willebrand Factor is a mechano-sensitive protein circulating in blood that mediates platelet adhesion to subendothelial collagen and platelet aggregation at high shear rates. Its hemostatic function andthrombogenic effect, as well as susceptibility to enzymatic cleavage, are regulated by a conformational change from a collapsed globular state to a stretched state. Therefore, it is essential to account for the conformation of the vWF multimers when modeling vWF-mediated thrombosis or vWF degradation. We introduce a continuum model of vWF unfoldingthat is developed within the framework of our multi-constituent model of platelet-mediated thrombosis. The model considers two interconvertible vWF species corresponding to the collapsed and stretched conformational states. vWF unfolding takes place via two regimes: tumbling in simple shear and strong unfolding in flows with dominant extensional component. These two regimes were demonstrated in a Couette flowbetween parallel plates and anextensional flow in a cross-slotgeometry. The vWF unfolding model was then verified in several microfluidic systems designed for inducing high-shear vWF-mediated thrombosis and screening for von Willebrand Disease. The model predicted high concentration of stretched vWF in key regions where occlusive thrombosis was observed experimentally. Strong unfolding caused by the extensional flow was limited to the center axis or middle plane of the channels, whereas vWF unfolding near the channel walls relied upon the shear tumbling mechanism. The continuum model of vWF unfolding presented in this work can be employed in numerical simulations of vWF-mediated thrombosis or vWF degradation in complex geometries. However, extending the model to 3-D arbitrary flows and turbulent flows will pose considerable challenges.

The Presence of Periodontitis in Patients with Von Willebrand Disease: A Systematic Review

The aim of this systematic review and meta-analysis was to analyze the available evidence on the assessment of periodontal disease in patients with von Willebrand disease (VWD). An electronic search in three databases (PubMed, Web of Science, and Scopus) was conducted by three independent reviewers to identify cross-sectional, cohort, and clinical trial studies. Studies considered eligible for this review were evaluated according to the quality and risk assessment tool proposed by the CLARITY Group at McMaster University. In order to analyze the possible correlation of VWD patients and periodontitis and their susceptibility to bleeding during the periodontal screening phase, periodontal parameters evaluated were probing pocket depth (PPD), bleeding on probing (BOP), gingival bleeding index (GBI), and periodontal inflamed surface area (PISA). After a screening of 562 articles, three articles were selected for the qualitative analysis. Within the limitation of our review, VWD patients are not more susceptible to periodontitis as compared with non-VWD patients. Nevertheless, bleeding on probing and gingival index needs to be carefully taken into consideration during periodontal screening of VWD due to the possible presence of false positives.

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

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

Patterns of von Willebrand Disease Screening in Girls and Adolescents With Heavy Menstrual Bleeding.

To estimate the frequency of von Willebrand disease screening and factors that affect screening frequency in a national sample of girls and adolescents with heavy menstrual bleeding. In this retrospective cohort study, we used a national claims database for privately and publicly insured patients between 2011 and 2013 for girls aged 10-17 years. Diagnostic criteria of heavy menstrual bleeding were the presence of one inpatient or two outpatient International Classification of Diseases, 9th Revision codes for heavy menstrual bleeding. We defined severe heavy menstrual bleeding as heavy menstrual bleeding plus an inpatient stay for menstrual bleeding, iron deficiency anemia, or blood transfusion. To assess whether patient- or facility-level characteristics affected screening, we performed logistic regression analysis including patient age, health care provider type seen at first visit for menorrhagia, patient residence in a metropolitan statistical area (proxy for urban vs rural inhabitance), and approximate travel time to the nearest hemophilia treatment center. We identified 23,888 postpubertal girls and adolescents with heavy menstrual bleeding (986 with severe heavy menstrual bleeding). Von Willebrand disease screening was performed in 8% of females with heavy menstrual bleeding and 16% with severe heavy menstrual bleeding. Younger age at diagnosis, commercial insurance, and living within a metropolitan statistical area were associated with higher screening rates. Patients who underwent testing for iron deficiency anemia had the highest likelihood of undergoing screening (odds ratio 7.08, 95% CI 6.32-7.93). Among patients living in a metropolitan statistical area, those 60 minutes or more from a hemophilia treatment center were less likely to undergo screening. Despite recommendations by the American College of Obstetricians and Gynecologists for more than 15 years, fewer than 20% of postpubertal girls and adolescents with heavy menstrual bleeding underwent screening for von Willebrand disease in this cohort. Increased clinician awareness and adherence to recommended screening recommendations may increase diagnosis of von Willebrand disease.

Von Willebrand Disease Screening in Women Undergoing Hysterectomy for Heavy Menstrual Bleeding

BackgroundBleeding disorders in women are under-recognized and under-treated. Women are equally as likely as men to have bleeding disorders other than hemophilia and are disproportionately affected by these diseases due to the bleeding challenges of menstruation and childbirth. The most common bleeding disorder identified in women is von Willebrand disease (VWD). Heavy menstrual bleeding (HMB) is the most common symptom in women with VWD, occurring in up to 93% of patients. Among women with HMB, the reported prevalence of VWD ranges from 5─20%. Women with VWD are also more likely to be diagnosed with hemorrhagic ovarian cysts due to ovulation-associated bleeding and endometriosis due to increased retrograde menstruation. As a result, women with bleeding disorders are more likely to undergo hysterectomy and also undergo hysterectomy at an earlier age than women without bleeding disorders. In 2001, the American College of Obstetrics and Gynecology (ACOG) recommended VWD screening prior to hysterectomy in women with HMB. The actual frequency of VWD screening in clinical practice is unknown.ObjectivesIn this study, we assess patterns of VWD screening in a nationally representative sample of women undergoing hysterectomies for HMB.MethodsWe used the Truven Health MarketScan® Research Databases which include the medical prescription claims of over 109 million covered lives as well as Medicaid data on 8.6 million patients from 14 states. The MarketScan Databases contain patient demographics, physician and facility claims and pharmacy claims. Procedure codes were used to identify women ages 10-44 years undergoing hysterectomy or hysterectomy alternative (HA) from 2011-2013. Subjects were required to have 12 months of continuous enrollment prior to surgery date. We utilized ICD-9 codes to categorize hysterectomy indications and only included women with a diagnosis of excessive bleeding as the indication for surgery. Women with fibroids, genital tract malignancy, and previously diagnosed bleeding disorders were excluded. We defined VWD screening as a laboratory claim for either VWF:Antigen and/or VWF:Activity within the 12 months preceding hysterectomy. To determine if patient and facility level characteristics impacted access to specialty hematology care and/or screening for VWD, we collected the following information: 1) known bleeding disorder diagnosis and/or endometriosis prior to surgery; 2) age; 3) whether patient was living in metropolitan statistical area (MSA; used as a surrogate marker for urban vs rural inhabitance); 4) number of miles and approximate travel time to nearest Hemophilia Treatment Center (HTC). We used ArcMAP® software to calculate distance between the MSA and nearest HTC. MSA data was only available for commercially-insured patients. (Figure 1) Logistic regression was used to assess factors related to the occurrence of VWD screening.ResultsWe identified 13,790 women who underwent hysterectomy/HA for HMB. We excluded 138 with known bleeding disorders leaving 13,652 women in our final analysis (Table 1). Of these, 74 (0.5%) were screened for VWD within 12 months preceding surgery. There were 2,000 women (15%) who underwent other coagulation tests, most commonly prothrombin time and partial thromboplastin time. We had MSA data on 11,557 commercially-insured women, of whom 72.4% lived within a MSA. Women living in a MSA were screened more often than those outside of a MSA (p=0.013). For those living within a MSA, the odds of being screened for VWD was lower in women with endometriosis (OR=0.54, 95% CI 0.31, 0.97; p=0.038) and women living >100 miles from the nearest HTC (OR=0.29, 95% CI 0.11, 0.81; p=0.017).DiscussionThis study demonstrated that despite ACOG expert recommendations, the frequency of VWD screening in a nationally-representative population of publically and commercially-insured women undergoing hysterectomy for HMB was very low. Greater distance from a HTC or a prior diagnosis of endometriosis further reduced the likelihood of VWD screening. It is important to increase awareness that a diagnosis of endometriosis does not rule out the presence of a bleeding disorder. This study brings to light the need for the hematology community to improve education and awareness among women's health providers in order to identify women with bleeding disorders and allow for optimal medical management of HMB prior to surgical consideration. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Variables That Affect Results of PFA-100 in a Group of Healthy Blood Donors in the Slovak Population

Abstract Background: The platelet function analyzer (PFA-100) is a system analyzing platelet function determined for detection of the functional inherited and acquired platelet disorders, screening of von Willebrand disease (vWD) and recently also considered as useful for monitoring of antiplatelet treatment. The PFA-100 test uses a high shear flow system to simulate in vitro the conditions to which platelets are subjected at the site of a damaged blood vessel wall. Aim of study: We decided to establish the reference intervals of PFA closure time (CT) in the Slovak population of healthy blood donors. Patients and methods: Fifty age and gender matched healthy blood donors were enrolled in the study. We investigated the relationships between PFA-100 CT, gender and ABO blood groups. Results: The reference intervals for CT measured on CEPI (collagen/epinephrine) and CADP (collagen/adenosine diphosphate) cartridge in 3.2% citrated blood were 86 - 199 sec. and 42 - 119 sec., respectively. Blood group O was associated with significantly longer CEPI CT (p&lt;0.05) compared to non - O groups. The prolongation of CADP CT in blood donors with blood group O was without significance. The influence of gender as another variable analyzed with CT has not been evaluated as statistically significant. Conclusion: PFA-100 CT should be interpreted carefully with consideration of both the patient’s clinical presentation and laboratory variables such as ABO blood group.

Application of a strain rate gradient microfluidic device to von Willebrand's disease screening.

Von Willebrand's disease (VWD) is the most common inherited bleeding disorder caused by either quantitative or qualitative defects of von Willebrand factor (VWF). Current tests for VWD require relatively large blood volumes, have low throughput, are time-consuming, and do not incorporate the physiologically relevant effects of haemodynamic forces. We developed a microfluidic device incorporating micro-contractions that harnesses well-defined haemodynamic strain gradients to initiate platelet aggregation in citrated whole blood. The microchannel architecture has been specifically designed to allow for continuous real-time imaging of platelet aggregation dynamics. Subjects aged ≥18 years with previously diagnosed VWD or who presented for evaluation of a bleeding disorder, where the possible diagnosis included VWD, were tested. Samples were obtained for device characterization as well as for pathology-based testing. Platelet aggregation in the microfluidic device is independent of platelet amplification loops but dependent on low-level platelet activation, GPIb/IX/V and integrin αIIbβ3 engagement. Microfluidic output directly correlates with VWF antigen levels and is able to sensitively detect aggregation defects associated with VWD subtypes. Testing demonstrated a strong correlation with standard clinical laboratory-based tests. Head-to-head comparison with PFA100® demonstrated equivalent, if not improved, sensitivity for screening aggregation defects associated with VWD. This strain rate gradient microfluidic prototype has the potential to be a clinically useful, rapid and high throughput-screening tool for VWD as well as other strain-dependent platelet disorders. In addition, the microfluidic device represents a novel approach to examine the effects of high magnitude/short duration (ms) strain rate gradients on platelet function.

Prevalence of Low VWF, VWD, and Isolated Collagen Binding Defects in Subjects Undergoing Evaluation for VWD

Laboratory testing of von Willebrand disease (VWD) continues to be a complicated and much debated subject. There are multiple tests recommended to assess varying aspects of von Willebrand factor (VWF) function, and no single test that identifies all VWD. In order to investigate the relative effectiveness of VWF laboratory testing, we examined a series of samples sent to a central reference laboratory for a VWD screen, which included VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), factor VIII activity (FVIII), and quantitative analysis of multimer distribution. Institutional review board approval was obtained to add testing for VWF binding to collagens 3, 4, and 6 (VWF:CB3, VWF:CB4, and VWF:CB6). Although no additional clinical information was available on the subjects, we presume that some degree of bleeding symptoms were present to drive clinical ordering of the VWD screen. A total of 882 subjects had results available for all the indicated VWF assays.With regard to VWF levels, 24% of subjects had VWF:RCo below the assay's lower limit of normal (54 IU/dL) and 16% had VWF:Ag below the assay's lower limit of normal (50 IU/dL), classified here as "Low VWF". Only 2% of subjects had either VWF:Ag or VWF:RCo < 30 IU/dL, consistent with the NHLBI's published guidelines on diagnosis of VWD. Only one subject (01.%) had an isolated defect in binding to collagen 3, defined as a VWF:CB/VWF:Ag ratio <0.5 and normal multimer distribution. However, 13 subjects (1.5%) had an isolated defect in binding collagens 4 and/or 6. Concordance between collagen 4 and 6 levels was observed for all subjects, although differences in collagen 3 vs collagens 4 and 6 were observed.With regard to multimer distribution, 2% of subjects had an abnormal multimer distribution including loss of high molecular weight or borderline abnormal multimer structure (defined as loss of the very highest molecular weight multimers). Of the subjects with abnormal multimer distribution, 82% had either abnormal VWF:RCo/VWF:Ag or VWF:CB/VWF:Ag ratios, leaving only 0.3% of the study population with an abnormal multimer distribution that would not have been suspected without formal multimer testing. Only 1% would be considered for a diagnosis of type 2A or type 2B. However, those subjects with loss of the very highest molecular weight multimers may represent acquired abnormalities related to sample processing defects rather than true structural abnormalities. 22 subjects (2.5%) had low VWF and a discrepancy between VWF:Ag and VWF:RCo suspicious for a diagnosis of type 2M VWD.Low VWF is a not uncommon finding in subjects undergoing evaluation for VWD. Although this data cannot confirm the degree of clinical symptoms present in the subjects under study, it is certainly consistent with the idea that specific screening for VWD is of high utility in patients presenting with bleeding complaints. A limitation of this study, however, is that laboratory data cannot be directly linked to phenotype, and it is possible that only patients at high risk of having VWD were screened and therefore the risk in the general population is much lower. Multimer defects were uncommon, and generally but not always confirmed by low collagen binding, which may be dependent upon the degree of structural abnormality, missing very subtle abnormalities. However, the use of two multimer-dependent screening tests (VWF:RCo and VWF:CB) improved the detection of multimer defects. In subjects with normal multimer distribution, defects in collagen 4 or 6 binding were far more common than defects in collagen 3 binding, and of equivalent frequency to low VWF levels. VWF collagen binding is not often included in the diagnostic workup for suspected VWD patients, but our data indicate that isolated defects in VWF binding to collagens 3 and 4 or 6 may be overlooked. Although this study did not confirm bleeding symptoms, our previously reported data indicate that subjects with VWF collagen binding defects may have increased bleeding symptoms. This data confirms the lack of a single screening test for VWD, and suggests that in order to fully exclude a diagnosis of VWD, a broad spectrum of assays is required. DisclosuresFriedman:CSL Behring: Consultancy; Instrumentation Laboratories: Consultancy; Novo Nordisk: Consultancy; Alexion: Speakers Bureau. Flood:Baxter: Consultancy; CSL Behring: Consultancy.

Use of a Pediatric Bleeding Questionnaire in the Screening of Von Willebrand Disease in Young Females at Menarche in the Primary Care Setting

Von Willebrand disease (VWD), the most common inherited bleeding disorder, is caused by deficiency or dysfunction in von Willebrand factor. Assessment of hemorrhagic symptoms is essential for early diagnosis, although bleeding histories are taken in a nonstandardized manner. Validated bleeding assessment tools provide objectivity in evaluating bleeding patterns of females at menarche and may improve provider confidence in screening for VWD. Utilizing a pretest/posttest design, in this project we implemented and evaluated the use of a pediatric bleeding questionnaire in eight pediatric primary care clinics for 3 months. Results indicate improved provider knowledge, confidence, and skills after implementation. The importance and quality of the tool were rated highly by the providers, while the ease of use was rated low. Providers were satisfied with the practice change and believed that it improved their clinical abilities. The use of this tool can improve VWD screening in this practice setting.

Screening of von Willebrand disease in Iranian women with menorrhagia.

Background:Menorrhagia is a common health problem in women, particularly those with bleeding disorders. Little is known about the course of menorrhagia or other bleeding symptoms in women with the most common congenital bleeding disorder, von Willebrand disease (vWD).Objectives:The aim of this study was to estimate the prevalence of vWD in women with diagnosed menorrhagia.Materials and Methods:In this cross-sectional study, a total of 460 consecutive patients, presenting menorrhagia, were analyzed. The initial screening and confirmation tests for the diagnosis of vWD included determination of prothrombin time (PT), partial thromboplastin time (PTT), bleeding time (BT), fibrinogen, factor VIII, vWF antigen, and vWF activity. A questionnaire was filled for every patient. The data were then analyzed using the SPSS software.Results:Mean age of our patients was 32.5 ± 10.6 years. The level of von Willebrand factor in 22.5% and von Willebrand activity in 19.6% of patients was abnormal. The prevalence of vWD among patients with menorrhagia was 24%.Conclusions:The high prevalence of vWD among our patients was the same as other previous reports, suggesting low awareness about this disease and under diagnosis of mild cases.

Comparison of a new chemiluminescent immunoassay for von Willebrand factor activity with the ristocetin cofactor-induced platelet agglutination method

Measuring von Willebrand factor (VWF) activity is essential for the diagnosis of von Willebrand disease (VWD). The VWF activity is usually assessed based on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging and has high intra- and inter-assay variabilities. A new automated chemiluminescent immunoassay VWF activity has recently become commercially available (HemosIL AcuStar von Willebrand Factor Ristocetin Cofactor Activity). The main objective of this study was to evaluate this new method and to compare it with the VWF:RCo assay as the reference method. We studied 91 samples, 18 healthy volunteers samples and 73 samples from patients (VWF:RCo level <50IUdL(-1) ): 29 type 1 VWD, 13 type 2A, 5 type 2B, 5 type 2M, 3 type 2N, 5 type 3, 4 type 3 under treatment, 5 type 3 carriers and 4 samples with other pathologies. The HemosIL AcuStar VWF:RCo assay was 96% sensitive and 100% specific for detecting VWF abnormalities. The good analytical performance, and the sensitivity and specificity of HemosIL AcuStar VWF:RCo to detect VWF deficiency renders it a suitable method for VWD screening.

Validation of a new panel of automated chemiluminescence assays for von Willebrand factor antigen and activity in the screening for von Willebrand disease

The diagnosis of von Willebrand disease (VWD) largely depends on the results of von Willebrand factor (VWF) antigen and activity. Recently, a new automated VWF:RCo assay on Acustar was developed. This assay panel for VWD also contains a new antigen (VWF:Ag) test. In this study, both chemiluminescence tests (HemosIL VWF:Ag and VWF:RCo) were evaluated. Imprecision, limit of detection (LOD), and linearity were evaluated. Method comparison (with VWF:Ag latex assay and VWF:RCo by aggregometry) was performed and diagnostic performance of the new test panel was examined. The imprecision was 7%, and the LOD was 0.2 IU/dL for both assays. Dilution series showed a large linearity for both HemosIL VWF:Ag (0-300 IU/dL) and VWF:RCo (0-200 IU/dL) and method comparison studies revealed good agreement with the currently used VWD panel. The new panel showed adequate diagnostic performance: diagnostic sensitivity was 100% and diagnostic specificity 82% compared with the VWF:Ag latex assay and VWF:RCo by aggregometry. In addition, the new HemosIL Acustar VWF:Ag and HemosIL Acustar VWF:RCo are more sensitive for VWD than the currently used assays. This new VWD test panel has adequate laboratory characteristics and allows fully automated and simultaneous analysis of the VWF:Ag and VWF:RCo.

The Prevalence of von Willebrand Disease and Significance of in Vitro Bleeding Time (PFA-100) in von Willebrand Disease Screening in the İzmir Region

Objective: von Willebrand disease (vWD) is the most common hereditary bleeding disorder. The purpose of this investigation was to determine the prevalence of vWD among adolescents in İzmir and to assess the sensitivity and specificity of PFA-100 as a screening method in detecting this disease.Material and Methods: Our study was conducted on adolescents in the city of İzmir between October 2006 and March 2007. A total of approximately 1500 high school students between 14 and 19 years of age were planned to be included in the investigation. Survey forms prepared for assessing hemorrhagic diathesis were completed by 1339 individuals (512 males, 827 females). The necessary laboratory tests were performed after having obtained written informed consent from 40 individuals suspected to have hemorrhagic diathesis.Results: Based on the von Willebrand factor antigen (vWF:Ag) and ristocetin cofactor activity (vWF:RCo) levels and bleeding symptoms, vWD type-1 was diagnosed in 14 individuals (4 males, 10 females; prevalence: 1.04%). The most common bleeding symptom in these patients was found to be epistaxis (10/14). Screening with PFA-100 revealed prolongation in both cartridges (Col/ADP and Col/Epi) in 3 of the 14 patients. PFA-100 was determined to exhibit 21.4% sensitivity and 100% specificity in the diagnosis of vWD.Conclusion: The PFA-100 device was found to have high specificity but to have exhibited low sensitivity. Therefore, its utilization as a screening test may be problematic in patients with mild type-1 vWD. Specific tests (vWF:RCo, vWF:Ag) are required for the definite diagnosis of vWD. However, further studies with a large number of patients are needed.Conflict of interest:None declared.