Von Willebrand Disease Testing Research Articles

Limited value of testing for factor XIII and α2-antiplasmin deficiency in patients with a bleeding disorder of unknown cause.

In patients with an increased bleeding tendency, extensive diagnostic blood testing is often performed. When results of tier 1 assays of primary haemostasis are normal, protocols recommend additional testing to rule out rare disorders including coagulation factor XIII (FXIII) and α2-antiplasmin (α2AP) deficiency. To evaluate the added diagnostic value of FXIII and α2AP levels in patients with a bleeding disorder of unknown cause (BDUC). A retrospective monocentre cohort study between August 2011 and August 2023 was conducted. In all patients with bleeding tendencies and normal diagnostic tests for von Willebrand disease and platelet function, FXIII and α2AP were measured. We included 158 consecutive patients; mean ISTH-BAT scores were 8.2 (SD±3.7) in children, 6.2 (SD±2.1) in men and 10.6 (SD±3.3) in women. Median age was 37 (range 5-79) years, 88.6% of patients were female. Patients displayed median FXIII activity of 111% (IQR=97-131) and median α2AP activity of 112% (IQR=103-119). Three (1.9%) patients had FXIII levels<50%, respectively 43%, 45% and 46%. Corresponding ISTH-BAT scores were 7, 12 and 14. No α2AP levels<60% was observed. No significant association was found between FXIII levels and ISTH-BAT scores. In our cohort of BDUC patients, no clinical relevant FXIII deficiencies were detected; absolute values were well above the 30% cutoff considered adequate for normal haemostasis. No α2AP deficiencies were detected. These data suggest that in BDUC patients, measuring FXIII or AP activity is of limited value.

The necessity of repeat testing for von Willebrand disease in adult patients with mild to moderate bleeding disorders

BackgroundIn patients with mild-to-moderate bleeding disorders (MBD), von Willebrand disease (VWD) is diagnosed at von Willebrand factor (VWF) levels ≤50 IU/dL. Although VWF levels are unstable, repeated testing for VWD diagnosis is not necessarily advised in recent guidelines. ObjectivesTo analyze the relevance of repeated VWF testing to diagnose VWD in patients with MBD. MethodsData of 277 patients with MBD from the Vienna Bleeding Biobank with at least 2 separate assessments of VWF antigen (VWF:Ag) and activity (VWF:Act) were analyzed. ResultsIn repeated VWF measurements, 36 patients (13.0%) had “changing” VWF levels (≤/>50 IU/dL), 27 (9.7%) had persistent levels ≤50 IU/dL (“pathologic”), and 214 (77.3%) had levels >50 IU/dL (“normal”). Of the 36 changing patients, 22 (61%) were diagnosed with VWD at baseline, whereas the others only met VWD diagnostic criteria at repeated measurements. Using logistic regression, we estimated a probability of change of 26.4% (95% CI, 12.5-47.4) at baseline VWF levels of 30 IU/dL, 50.8% (95% CI, 35.6-65.8) at 50 IU/dL, 18.8% (95% CI, 12.3-27.6) at 60 IU/dL, and 1.2% (95% CI, 0.3-4.9) at 80 IU/dL. Baseline VWF was a strong predictor for changing status (Χ2 = 49.9; P < .001), while age, sex, Vicenza score, and blood type O had limited added value (Χ2 = 5.1; P = .278). Baseline VWF:Ag or VWF:Act cutoffs of 80 IU/dL had negative predictive values of 98.1% and 99.1% for changing status, respectively. ConclusionOur data emphasize an overlap between patients with VWD and MBD with bleeding disorder of unknown cause and underline the need for repeated VWF testing, especially in patients with VWF levels <80 IU/dL.

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.

Acquired Von Willebrand Disease Associated with Hematologic Malignancies: Case Series and Literature Review

Objective: To describe a single institution experience of AvWD of the spectrum of presentation in hematologic malignancies. Introduction: Acquired von Willebrand disease (AvWD) is a rare acquired bleeding disorder characterized by mucocutaneous bleeding and functional alterations in von Willebrand factor (vWF). AvWD can be caused by numerous conditions but we are going to focus on those associated with hematologic malignancies. The pathogenic mechanisms responsible for the vWF abnormalities can include abnormal clearance due to binding of paraproteins, inhibition of vWF, adsorption to the surface of platelets, proteolysis from increased fluid shear stress, and decreased synthesis. Methods: Clinical review of 4 cases of AvWD at a tertiary academic medical center from January 2016 to January 2022. Results: Case 1: 57-year-old female with history of chronic thrombocytosis of 1.6 million and was diagnosed with a JAK2 V617F mutation positive essential thrombocythemia and concurrent iron deficiency anemia. She was placed on low dose aspirin for thromboprophylaxis and presented with hematochezia with a drop in hemoglobin from 9.7g/dL to 4.3g/dL, platelets were 857k/uL. At that time her aPTT was mildly elevated at 37.0 (normal 36.5) This prompted testing for von Willebrand disease which showed low vWF activity 50% and vWF GP I binding activity 47% with normal vWF antigen activity 82% and factor VIII clotting activity of 100 IU/ml. Aspirin was held and hydroxyurea initiated at 1000mg daily with clinical response. Coagulation testing including aPTT and vWF antigen, Activity and multimers normalized after cytoreduction of her platelets with hydrea. Case 2: 75-year-old male with history of stroke on aspirin. We saw the patient for erythrocytosis and made the diagnosis of JAK 2 V617F mutation positive polycythemia rubra vera. Phlebotomy was initiated however, he presented with large ecchymoses at the venipuncture sites following phlebotomy. Testing showed quantitative vWF and factor VIII were normal, abnormal GPIbM: vWF ratio and loss of highest molecular weight multimers. He was maintained on hydroxyurea 1500mg daily for target hematocrit of 40 g/dL and low dose aspirin thromboprophylaxis without recurrent bleeding. Case 3: A 68-year-old female who we were following with a history of an IgM monoclonal gammopathy of undetermined significance (MGUS) reported mild ecchymosis on the extremities. Testing showed low factor VIII level of 34% and low vWF antigen and activity at 29% and 22%, and normal vWF multimers. She has been observed without any therapy given lack of clinically significant bleeding. Three years later, she has now developed of cytopenias and bone marrow biopsy showed 30 - 40% lymphoplasmacytic infiltrate consistent with progression to Waldenström Macroglobulinemia. Case 4 60 year-old-male with history of an IgG lambda MGUS who presented with new onset recurrent melena without a source of bleeding found on endoscopy. Testing showed decreased vWF antigen 30% and vWF activity 21%, normal factor VIII activity 69% and all multimers decreased consistent with AvWD from his known MGUS. His recurrent mucosal bleeding was managed with weekly Humate P. Revlimid 10mg per day was initiated for MGUS. Two months later, his indices improved with normalized VWF multimers and VWF antigen 70% and factor VIII activity 142%, and with now only mildly decreased VWF activity at 48%. Recurrent bleeding ceased. Conclusions: Patients with hematologic malignancies may present with mucocutaneous bleeding which may mimic congenital vWD however, AvWD should be considered in this population of patients. In addition, patients with AvWD can present with varying degrees of bleeding which might be mistaken for platelet dysfunction due to the underlying malignancies or the addition of aspirin or anticoagulation. One must maintain high clinical suspicion for AvWD with new onset bleeding in setting of known myeloproliferative or lymphoproliferative disorder. vWF antigen, activity, factor VIII activity and multimer testing should be obtained to secure the diagnosis. Treatment of the underlying disorder will result in clinical and laboratory improvement.

To Repeat or Not Repeat, That Is the Question: Von Willebrand Testing in Adolescent Girls with Heavy Menstrual Bleeding

Heavy menstrual bleeding (HMB) is often the initial manifestation of a bleeding disorder in adolescent females. Von Willebrand disease (VWD) is the most common bleeding disorder, yet diagnosing VWD in HMB is challenging given that menstruation, acute illness, and physiologic stress all elevate von Willebrand factor (VWF) laboratory values. Thus, the interpretation of initial VWF results may be challenging, and the need for repeat VWF testing in this population may be unclear. The aims of this study were to understand VWD diagnostic testing patterns in adolescent females evaluated within the Texas Children's Hospital (TCH) network and to develop a prediction model to determine whether repeat testing was indicated based on initial VWF testing results. Female patients aged 9 to 21 years who had any VWF laboratory test over a 5-year period (January 1, 2017 through December 31, 2021) at a TCH facility (greater Houston metroplex) were identified. Data collection included patient demographics, VWF-related testing (antigen and activity [ristocetin cofactor or glycoprotein Ib]), factor VIII activity, hemoglobin concentration and serum ferritin. Both initial and subsequent laboratory evaluations were collected. The site of clinical testing was also identified, including both acute care settings (emergency department, inpatient, and critical care), and outpatient settings (adolescent medicine, gynecology, hematology, otolaryngology, other outpatient TCH primary care clinics). To ensure that subsequent laboratory testing was not mistaken as the initial testing within the cohort, patients who underwent VWF laboratory testing from 2010 to 2016 were excluded. VWF levels obtained after the administration of VWF replacement products were also removed from the data set. Based on the ASH ISTH NHF WFH 2021 guidelines on the diagnosis of VWD, and with the presumption that adolescents with HMB met the criteria for abnormal bleeding, we analyzed the need to repeat VWF testing to identify any patient with a low VWF antigen level consistent with Type 1 VWD, defined as <50%. A Bayesian linear regression model was developed to predict follow-up VWF antigen levels using the initial levels. Prediction intervals were analyzed to identify thresholds for patients who may not require retesting. This study was approved by the Baylor College of Medicine Institutional Review Board. A total of 6,125 adolescent females underwent VWD testing at a TCH facility during the study period; 1,204 (19.7%) had repeat VWF antigen values performed and were included in the analysis (TABLE). Of those, 1,037 subjects (86.1%) had normal VWF values (≥50%) on both initial and repeat testing. Seventy-five subjects (6.2%) had low VWF antigen values on both initial and repeat testing. Ninety-two subjects had discrepant initial and repeat testing. Forty-seven (3.9%) had low initial VWF antigen values that normalized on subsequent testing. Forty-five (3.7%) had normal initial VWF values that subsequently fell below 50%. Based on our prediction model, in subjects with initial VWF antigen values of ≥80% there was ≥97% probability of having normal repeat VWF values. Values of ≥100% carry a 99.4% probability of having normal repeat VWF testing (FIGURE). No association was identified between age and VWF antigen level. Subjects assessed in outpatient adolescent medicine or gynecology clinics were more likely to have low VWF values (on any testing) whereas subjects with normal values were more frequently assessed in the acute care settings (P<0.001). The median serum ferritin and hemoglobin values in the cohort were 13 ng/ml and 12.8 g/dl, respectively, without a significant difference between those with normal versus low VWF antigen values. Repeat testing in adolescent females whose initial VWF antigen testing values are 80% and higher is unlikely to identify more patients with VWF values below 50%. In this cohort, subjects undergoing hemostatic evaluation, presumably for HMB, by adolescent medicine or gynecology providers were more likely to identify abnormal VWD testing compared to the acute care setting. Iron deficiency screening should be considered for all adolescent females with HMB and not just those girls with a confirmed bleeding disorder. Additional studies are needed to determine the effects of iron deficiency and anemia on VWD laboratory testing in adolescent females with HMB and to validate the accuracy of the prediction model. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prevalence of Heavy Menstrual Bleeding and Use of Hormonal Therapy Among Women Type 1 Von Willebrand Disease from the Zimmerman Program

Background: Women with von Willebrand disease (VWD) experience substantial reproductive tract bleeding, including heavy menstrual bleeding (HMB). Over 80% of women with VWD experience HMB resulting in morbidity from decreased quality of life, lost productivity, and iron deficiency. Hormonal birth control is a standard treatment and can elevate VW activity (RCo/GPB1M) and antigen (Ag) levels. Little is known about the impact of such therapy on bleeding assessment tools (BATs). We hypothesized that women on hormonal therapy (HT) would have lower ISTH-BAT scores and higher VWD levels than those not on HT. Women who participated in the Zimmerman Program (PPG) for the Molecular and Clinical Biology of VWD, a natural history study (NHLBI HL081588), had demographic, medication history, and laboratory samples collected. We sought to identify differences in patient, disease-specific factors, and BATs between type 1 VWD women on HT and those not on HT. Methods: Women with type 1 VWD and reported menstrual history were selected from the PPG. Women were split into those taking HT (OCPs, injectable progestins, hormone replacement therapy, intravaginal devices, and IUDs) vs. those who were not. Women >50 years of age were excluded from the group analysis due to their assumed postmenopausal status. Descriptive statistics were calculated to characterize the demographics, VWD testing (VWF:Ag, VWF:RCo, GPIbM), and ISTH-BATs (total, HBM, and PPH) of the two groups. Continuous variables were compared between groups using two sample t-test and categorical variables by Fischer's exact test. A two-sided p-value of< 0.05 was considered statistically significant. Results: In the full cohort, 269 women answered yes to experiencing menstrual cycles. The group was predominantly pediatric/young adult with a mean age of 25.3 years (range 11-76). Whites comprise 86% of subjects. Women were further defined by disease laboratory testing with 186 women (69.1%) diagnosed as VWF:Ag 0.3-0.5 IU/mL, 57 women (21.2%) VWF:Ag <0.3 IU/mL, and 26 women (9.7%) clearance type VWD (genetic result). The mean VWF:Ag for the entire cohort was 0.37 IU/mL (Standard Deviation 0.14 IU/mL). The mean VWF: RCo was 0.36 IU/mL (SD 0.15 IU/mL). The ISTH-BAT scores ranged from 0-29, with a mean of 7.6 (SD 5.1). An evaluation of the HMB domain of the ISTH-BAT demonstrated that 94% (253) of women reported HMB with >1 point (on a 4-point scale) overall, 47% (119) of whom reported severe HMB with 3 or 4 points. Of the 269 women, 108 were taking HT at enrollment. The types of HT included OCPs (71), medroxyprogesterone acetate (11), levonorgestrel IUD (11), contraceptive implant (3), and etonogestrel/ethinyl estradiol vaginal ring (1). After excluding women with presumed postmenopausal status, we identified 105 women on hormonal therapy and 143 who were not. Graph 1 provides an overlay of the ISTH-BAT scores by hormone treatment status. Table 1 demonstrates the demographic and disease features of the two groups. On average, women on HT were younger, 20.7 years vs. 24.5 years (p= 0.003), than those who were not. Other disease characteristics, including disease subtype, VWF laboratories (VWF:Ag, VWF: RCOF, VWF GPIbM), and ISTH-BAT HMB and PPH specific domains were not significantly different between the groups. Higher total ISTH-BAT scores were observed for women not on HT (7.4± 5.1) compared to those who were (6.8± 4.2); however, the difference was not statistically significant. Conclusions: For women with type 1 VWD, HMB is widespread, affecting 94% of the subjects enrolled in the PPG. Hormone therapy was common, with 47% receiving treatment. Apart from age, there were no significant differences in the disease characteristics or BATs between women with type 1 VWD who are and are not receiving hormone therapy in this cohort. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Diagnostic Testing for von Willebrand Disease: Trends and Insights from North American Laboratories over the Last Decade.

Accurate diagnosis of von Willebrand disease (VWD) depends on the quality, precision, and variability of the laboratory assays. The North American Specialized Coagulation Laboratory Association (NASCOLA) is a provider of external quality assessment (EQA) for approximately 60 specialized coagulation laboratories in North America. In this report, NASCOLA EQA data from 2010 to 2021 are reviewed for trends in methodology and precision among various assays. In particular, recent ASH ISTH NHF WFH (American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Hemophilia Federation) guidelines for diagnosis of VWD are reviewed in light of EQA data. In contrast to other geographic regions, laboratories in North America predominantly use three-assay screening panels (antigen, platelet-binding activity, and factor VIII [FVIII] activity) rather than four-assay panels (antigen, platelet-binding activity, FVIII activity, and collagen-binding activity). They also use latex immunoassays rather than chemiluminescence immunoassays, and the classic ristocetin cofactor (VWF:RCo) assay and monoclonal antibody (VWF:Ab) assay to assess VWF platelet-binding activity over newer recommended assays (VWF:GPIbM and VWF:GPIbR). Factors that may be influencing these North American practice patterns include lack of Food and Drug Administration approval of the VWF:GPIbM, VWF:GPIbR, collagen binding assays, and chemiluminescence methodologies, and the influence of the 2008 National Heart, Lung, and Blood Institute guidelines on laboratory practice. Lastly, systems-based solutions are urgently needed to improve the overall accuracy of laboratory testing for VWD by minimizing preanalytical variables and adopting assay standardization.

Comparing the quality of testing for von Willebrand disease in different geographic localities.

Comparing the quality of testing for von Willebrand disease in different geographic localities.

Successful Treatment with Emicizumab of Patient with Type 2N Normandy and Severe Hemophilia a

It is unusual to have both Type 2N VWD and severe hemophilia A. Type 2N (Normandy) von Willebrand Disease (VWD) is an uncommon recessive disorder resulting in a defect in the binding site of von Willebrand Factor (VWF) with factor VIII. Factor VIII plasma levels are low due to rapid clearance. Our patient has severe hemophilia A (factor VIII <1%; Inversion 22) with no history of inhibitors and is heterozygous for a known pathogenic mutation (c2560C>T; p. Arg854Trp) Type 2N “Normandy”. He benefited from the use of HEMLIBRA® (Emicizumab-kxwh, Genentech) a humanized bispecific monoclonal antibody with a long half-life independent of VWF interaction.The patient was diagnosed at 11 months old with excessive bleeding from his frenulum and began episodic standard factor VIII. He had 10 bleeds including knees, arms and hamstring before starting prophylaxis at 3 yrs. of age. On ADVATE 50 units/kg/dose twice a week he had nose bleeds, soft tissue bleeds, and joint bleeds. At 11 yrs. of age, the nose bleeds increased daily. VWD testing revealed VWF activity 25%, VWF Antigen 42%, Factor VIII <1% and Normal Multimers with Type 2 Normandy genotype. ALPHANATE® (Anti-hemophiliac factor/von Willebrand factor complex (human), Grifols) prophylaxis was started to address mucosal bleeding however the right elbow synovitis progressed to right elbow contracture and bone cyst on MRI. He returned briefly to ADVATE® 50 units/kg MWF to every other day prophylaxis with continued intermittent bleeding in right elbow joint. With the diagnosis of Type 2N, and the availability of VONVENDI ® (Recombinant von Willebrand factor, Takeda), he was placed on ADYNOVATE® (Antihemophilic Factor Recombinant PEGylated, Takeda) daily and VONVENDI® every 3rd day starting at 14 yrs. old. The combination of ADYNOVATE® every 12-24 hours with VONVENDI® daily to every other day improved his acute bleeding episodes including his nose bleeds (Half-life ADONYVATE®+VONVENDI® 9.25 hr. vs. Half-life ADVATE® 5.5 hr.). The patient continued to participate in high-risk activities such as playing on trampoline which contributed to his injuries but his family felt the treatment was better than previous therapies.After considering the treatment burden of 2 types of factors more than 5 times a week and progression of synovitis in right elbow joint, the patient was started on HEMLIBRA® with weekly subcutaneous injections. Four weeks of loading dose (3 mg/kg/dose) was followed by once per week prophylaxis at standard dosing 1.5 mg/kg weekly. The first bleeding episode on HEMLIBRA® was reported after tooth restoration October 2019. After receiving both ADYNOVATE® and VONVENDI® pre-op, he developed swelling with suspected hematoma at the angle of his jaw about 4 days post-op treated successfully with ADYNOVATE® /VONVENDI®. In April 2020, he had right elbow pain stereotypic of a joint bleeding episode after yard work which was treated successfully with ADYNOVATE® /VONVENDI®. No report of severe nosebleeds.To our knowledge this is the first example of successful use of HEMLIBRA® in a patient with Type 2N VWD and severe hemophilia A. It is unclear why the ALPHANATE® was not clinically effective however the combination of VONVENDI® and ADYNOVATE® provided improved hemostasis with frequent infusions and high cost before the start of HEMLIBRA®. HEMLIBRA once a week has significantly reduced the treatment burden and improved bleeding prevention. The genotype of this patient is unusual however this approach may be successful in other types of VWD that result in significant bleeding phenotype. [Display omitted] DisclosuresBryant: Novo Nordisk: Consultancy, Honoraria; Bristol Myers Squib: Consultancy, Honoraria; Hema Biologics: Consultancy, Honoraria. Carr: Genentech: Speakers Bureau; Bayer: Speakers Bureau; Medexus: Speakers Bureau.

Why is Misdiagnosis of von Willebrand Disease Still Prevalent and How Can We Overcome It? A Focus on Clinical Considerations and Recommendations.

Despite von Willebrand disease (VWD) being the most common inherited bleeding disorder, its accurate diagnosis is frequently shrouded by diagnostic pitfalls. VWD is frequently under-diagnosed, over-diagnosed and misdiagnosed, leading to significant avoidable patient morbidity and health care system burden. At the heart of this dilemma lies the heterogeneity and complexity of von Willebrand factor (VWF) and associated defects, and the necessity of coalescing clinical and laboratory features to obtain an accurate diagnosis. Common pitfalls include poor clinical and scientific understanding and familiarity with VWD, incomplete clinical history and lack of routine use of standardised bleeding assessment tools (BAT), difficulty in accessing a comprehensive repertoire of laboratory tests, significant pre-analytical, analytical and post-analytical issues, and lack of expertise in laboratory testing and interpretation. Errors, resulting in under-diagnosis, over-diagnosis, and misdiagnosis of VWD, are presented and discussed. Strategies to minimise errors include better education of clinicians and laboratory staff on VWD, routine use of validated BAT, utilising a comprehensive gamut of laboratory investigations according to a standardised algorithm, and repeating testing to minimise pre-analytical errors. Recommendations on appropriate patient selection for VWD testing, how VWD should be investigated in the laboratory, and how to ensure test results are accurately interpreted in the correct clinical context are detailed.

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

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

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

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

The Discordance between Offsite to Onsite Testing for Von Willebrand Disease in Post-Menarchal Females: A Multi-Center Study

The Discordance between Offsite to Onsite Testing for Von Willebrand Disease in Post-Menarchal Females: A Multi-Center Study

Update on Molecular Testing in von Willebrand Disease

Diagnosis of von Willebrand disease (VWD) depends on personal and family history of bleeding and confirmatory laboratory testing. Currently available phenotypic tests for VWD contain potential sources for error that may distort results. Despite an exponential growth of information about the von Willebrand factor gene (VWF), the role of molecular diagnosis in VWD is still controversial. Due to the complexity and high cost of conventional molecular analyses, some investigators have recommended limiting this approach to distinguish suspected type 2N VWD from hemophilia A, type 2B from platelet-type VWD, and the exploration of type 3 VWD. New genetic methodologies and approaches are becoming available, but there is still some reluctance for their implementation in VWD diagnosis. This article discusses the pros and cons of molecular testing in VWD considering the experience obtained through the multicenter project "Molecular and Clinical Profile of VWD in Spain (PCM-EVW-ES)."

Rethinking internal quality control and external quality assessment for laboratory diagnostics of von Willebrand disease

von Willebrand disease (VWD) is recognised as the most common congenital bleeding disorder, and an acquired form named von Willebrand syndrome (AVWS) may arise in a variety of disease states. Thus, laboratory testing for VWD and AVWS represents a key diagnostic activity of hematology facilities performing advanced hemostasis diagnostics. VWD and AVWS arise due to deficiency and/or defect(s) in the adhesive plasma protein called von Willebrand factor (VWF). VWF represents a key element of primary hemostasis, and also contributes to secondary hemostasis. Thus, deficiency and/or defects in VWF, either congenital or acquired, leads to a bleeding diathesis in affected individuals. A wide variety of laboratory tests may be performed to investigate, diagnose or exclude VWD/AVWS, including screening assays, more complex functional assays, and also molecular analysis. Thus, VWD testing now incorporates a variety of processes, and potential methodologies. Internal quality control (IQC) and external quality assessment (EQA) is critical to ensure the quality of laboratory testing, but is made difficult in VWD diagnostics by the nature and variety of the tests available, and the heterogeneity of VWD/AVWS. The current review looks at laboratory testing for VWD/AVWS from the perspective of IQC and EQA, and considers some novel approaches to ensure the accuracy and quality of this activity in the future diagnostics landscape.

Initial Evaluation of Adolescent Females Hospitalized with Heavy Menstrual Bleeding

Background: Heavy menstrual bleeding (HMB) in adolescents can be severe and life-threatening. Up to 30% of young women who are hospitalized with anemia due to HMB have a bleeding disorder. Guidelines from the American College of Obstetrics and Gynecology (ACOG) and the National Heart, Lung, and Blood Institute (NHLBI) recommend evaluation for bleeding disorders in such patients. ACOG recommendations include testing for von Willebrand disease (VWD) and specify that consultation with a hematologist may help in interpreting results. NHLBI recommends testing for vWD be done in conjunction with a hematologist. As von Willebrand factor is an acute phase reactant, testing when patients are severely anemic and bleeding may not provide accurate results. ACOG guidelines do not include testing for platelet function disorders (PFD), though PFD may be as prevalent as VWD in females with HMB. Early and accurate diagnosis of bleeding disorders is important for health and quality of life, yet limited data exists on the diagnostic evaluation for bleeding disorders in adolescent females hospitalized for HMB.Objectives: To evaluate the diagnostic evaluation of bleeding disorders in adolescent females hospitalized for HMB.Methods: A retrospective, single center chart review of female patients aged 9-21 years hospitalized for HMB and anemia at a tertiary care children's hospital from January 1, 2000 until December 31, 2017 was done. HMB was defined as menses ≥7 days in length, use of 8 or more pads or tampons per day during menses, pictorial bleeding assessment chart (PBAC) score greater than 100, or symptomatic anemia. Patients were identified from our Hemophilia Treatment Center (HTC) registry, review of patients seen at a comprehensive clinic staffed by pediatric hematologists and gynecologists for adolescent females with HMB and bleeding disorders, and by an Electronic Medical Record (EMR) query of admission and discharge diagnoses of HMB and anemia. Data obtained included clinical features, diagnostic evaluation, and laboratory results.Results: 118 patients hospitalized for HMB and anemia were included. Inpatient Hematology consult or outpatient referral occurred in 68 (58%) of the patients; 60/68 (88%) had a bleeding disorder evaluation completed. 34 patients had a hematologic disorder. PFD was the most common (15/34; 44%) followed by VWD (9/34; 26%). 42% (50/118) of the patients did not have a Hematology consult or outpatient referral (Table 1). While hospitalized for HMB and anemia, 29 of the 50 patients had testing for vWD performed and only 4/29 (14%) had testing repeated as an outpatient once hemoglobin normalized. No patients tested for VWD while inpatient had results consistent with the diagnosis. Platelet function testing was performed in 10/50 patients using the platelet function analyzer (PFA-100) in 8 patients and platelet aggregometry in 2 patients.Conclusions: Despite national guidelines and the presence of known risk factors such as HMB since menarche and HMB causing severe anemia, the hematology service was not involved in the diagnostic process for a significant number of adolescent females. In these patients, testing often occurred while patients were hospitalized and was not repeated. Testing for platelet function disorders occurred infrequently and mainly consisted of the PFA-100 which lacks sensitivity and specificity. When patients were evaluated by Hematology and tested for bleeding disorders, a large proportion had a bleeding disorder, of which PFD were most common. This study demonstrates the need for standardization of the evaluation of adolescent females hospitalized for HMB. Guidelines should be updated to include testing for PFD. Hematologists should be involved when females are hospitalized for HMB and anemia. [Display omitted] DisclosuresCarpenter:Genentech Incorporated: Membership on an entity's Board of Directors or advisory committees; Nationwide Children's Hospital: Speakers Bureau; Bayer: Honoraria; Kedrion Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Novo Nordisk Pharmaceuticals, Inc: Consultancy; HEMA Biologics: Consultancy; American Academy of Pediatrics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novo Nordisk: Consultancy; National Hemophilia Foundation (Impact Education): Speakers Bureau; Kane County State's Attorney: Consultancy; CSL Behring: Speakers Bureau; 4th Judicial District Attorney's Office- Colorado: Consultancy; Kedrion Biopharmaceuticals: Consultancy.

Von Willebrand disease in the United States: perspective from the Zimmerman program.

This article will discuss the diagnosis and management of von Willebrand disease (VWD) in the United States and results from the Zimmerman Program, a national study of VWD. An algorithm is presented to show how we currently approach diagnostic testing for VWD, including the potential replacement of the ristocetin cofactor assay with a new von Willebrand factor (VWF)-GPIb binding assay. Results from the Zimmerman Program type 1 cohort are presented, including the findings that genetic defects in the VWF gene are most common with VWF levels <30 IU/dL, but bleeding symptoms were present across the entire cohort regardless of VWF level. Typical management of VWD patients is also discussed, including the use of desmopressin and VWF concentrates. Despite these advances, there remain several areas of VWD where more research is required to optimize treatment.

Challenges in the laboratory diagnosis and management of von Willebrand disease in South Africa

Background: South African von Willebrand disease (VWD) care is challenged by the lack of laboratory testing standardisation, lack of national clinical guidelines, limited undergraduate exposure to bleeding disorders and limited pharmacological resources. As the only reference testing facility performing VWD confirmatory testing, our experience in the diagnosis of the majority of VWD cases in South Africa has highlighted many areas where improvements are desperately needed. Methods: We conductedd a retrospective audit of 250 VWD cases at our laboratory where we calculated the percentage misdiagnoses should only the von Willebrand factor (VWF) levels and the ristocetin cofactor activity assays be used. Results: We have shown that performing a limited panel of VWD testing (VWF antigen and ristocetin cofactor activity only) could lead to the misdiagnosis of VWD in up to 77% of cases analysed at our laboratory. If the multimeric analysis was to be included in the diagnostic setup, together with the limited panel, still 20% of patients would be misdiagnosed. The underdiagnosis and under-reporting of VWD greatly underestimates the burden of the disease and the impact on the healthcare system. Conclusions: Future advancements in VWD care in South Africa should be focused on correcting these shortcomings.

Laboratory Diagnosis of von Willebrand Disease

Von Willebrand disease (VWD) is considered the most common congenital bleeding abnormality in the world and an accurate diagnosis is often very challenging. Clinical laboratories usually provide screening assays along with more complex assays to aid clinicians with the diagnosis. These assays measure different properties and activities of von Willebrand factor. They may be adversely affected by numerous preanalytical variables and often have variable performance characteristics that may contribute to an inadequate interpretation. This review describes methods used in the laboratory for diagnosing VWD and basic mechanisms of each of these assays. A thorough understanding of the assays and associated preanalytical variables in VWD testing is essential for accurate diagnosis. ABBREVIATIONS:ADAMTS13 - a disintegrin and metalloproteinase with a thrombospondin type 1 motif, DDAVP - 1-desamino-8-D-arginine vasopressin, EC - endothelial cell, VWD - von Willebrand disease, VWF - von Willebrand factor, VWF:Ag - von Willebrand factor antigen, VWF:CBA - von Willebrand factor collagen binding assay, VWF:RCo - von Willebrand factor ristocetin cofactor activity

Diagnosis or Exclusion of von Willebrand Disease Using Laboratory Testing.

von Willebrand disease (VWD) is a common bleeding disorder diagnosed based on clinical features and following laboratory testing. VWD is due to deficiencies or defects in the plasma protein von Willebrand factor (VWF), a large adhesive protein with multiple activities. Laboratory testing therefore centers on assessment of VWF protein level using VWF antigen (VWF:Ag), as well as assays that measure VWF activity, most notably platelet glycoprotein (GP) Ib and collagen binding (VWF:CB) activities. Decreases in VWF:Ag and VWF activities, as well as the pattern of such changes, help define VWD and its type. Classically, the most often used assay for measuring GPIb binding activity was the ristocetin cofactor assay (VWF:RCo), which historically measured agglutination of fixed human platelets by VWF in the presence of ristocetin. This assay is now often replaced or supplemented with other assays based on binding of VWF to recombinant GPIb, generally without the use of platelets, and with or without ristocetin. This chapter briefly reviews laboratory tests for VWD, as well as recommended approaches to use of such assays to help diagnose or exclude VWD in patients showing clinical features.