Von Willbrand Disease. What's new ?.pptx

Von Willbrand Disease

1. VWD assessment and severity prediction ,what's new ? By Aya Omar

2. Mahalakshmi, a., Priya, a. & Chander, k. A. 2022. A case report on von willebrand’s disease. Favaloro , e. J., Mohammed, s., Vong , r., Oliver, s., Brennan, y., Favaloro , j. W. & Curnow, j. J. H. 2021. How we diagnose 2M von willebrand disease (VWD): use of a strategic algorithmic approach to distinguish 2M VWD from other VWD types. 27, 137-148. von Willebrand disease (VWD) von Willebrand disease (VWD) is the most common inherited bleeding disorder caused by defects in amount, structure or function of von Willebrand factor (VWF). VWD prevalence estimates range from ∼ 1 in 100 to 1 in 10 000.

3. Quantitative Type 1 VWD involves a partial deficiency of von Willebrand factor (VWF), with the diagnostic cutoff levels for this type being a topic of ongoing debate. Qualitative is a heterogeneous group with qualitative VWF defects. Subtypes are 2A, 2B, 2M and 2N. Quantitative Type 2 VWD Type 3 VWD is a complete deficiency of VWF Kalot, m. A., Husainat , n., El alayli , a., Abughanimeh , o., Diab, o., Tayiem , s., Madoukh , b., Dimassi , a. B., Qureini , a. & Ameer, b. J. B. A. 2022. Von willebrand factor levels in the diagnosis of von willebrand disease: a systematic review and meta-analysis. 6, 62-71. VWD classification

4. Type 1 C VWD type 1C (C for clearance) is characterized by a significant increase of VWF clearance, leading to low VWF levels with a significantly shortened half-life. Patients with VWD type 1C are identified by an increased ratio of VWFpp to VWF:Ag because only the mature VWF molecule is cleared more rapidly.

5. VWD Diagnosis

6. Due to the variability of the disease and the difficulties in standardizing diagnostic tests, diagnosing VWD and distinguishing different types , in practice, can be complex. However, precise classification and severity assessment have important therapeutic consequences . VWD Diagnosis

7. ASH ISTH NHF WFH 2021 guidelines for the diagnosis of VWD

8. VWD Diagnosis The first step is the history and clinical examination. Bleeding symptoms evaluation is critical in the clinical assessment of patients who are referred for a possible bleeding disorder, especially those with mild bleeding diatheses before starting complex and expensive laboratory studies.

9. There are multiple different assays that is used to assess VWF functional activity. The traditional one is called VWF ristocetin cofactor assay VWF:RCO Newer assays, that measure the platelet-binding activity of VWF, for e.g VWF:GPIbM , VWF:GPIbR , should be used over the ( VWF:RCo ) for the diagnosis of VWD. VWF activity assays

10. Platelet-binding activity of VWF activity

11. This VWF activity assays use recombinant gain‐of‐function mutant GPIb fragments, allowing spontaneous binding of VWF to the mutant GPIb without ristocetin; removes the unphysiological ristocetin. VWF:GPIbM has an exceptional coefficient of variation, a lower limit of detection that is more sensitive, and an outstanding correlation with the VWF:RCo test ( Szederjesi et al., 2018 ). von Willebrand factor activity using (VWF:GPIbM)

12. The VWF:CB test evaluates the ability of VWF to bind to collagen, which reflects the presence and functionality of the larger, more hemostatically active VWF multimers. VWF:CB to VWF antigen (VWF:CB/ VWF:Ag ) ratios of less than 0.6 or 0.7 have been considered to indicate abnormal results, with ratios above that presumed to represent a normal multimer distribution. VWF collagen binding (VWF:CB)

13. VWF acts as a carrier protein for coagulation Factor VIII (FVIII), protecting it from rapid clearance from the circulation. In VWD Type 2N, there is a defect in the VWF's ability to bind FVIII, leading to FVIII deficiency. The VWF:FVIIIB assay measures the ability of VWF to bind FVIII. This assay uses a modified ELISA technique. Patients with VWD Type 2N will have a normal VWF:Ag and a normal VWF activity , but they will show a marked decrease in FVIII levels and in VWF:FVIIIB assay. VWF FVIII binding (VWF:FVIIIB)

14. Difficulties in VWD diagnostic tests

15. Difficulties in VWD diagnostic tests Time consuming to reach final diagnosis (see the upcoming chart). Reagents stability and cost requires sample collection and storage to avoid wasting the reagents (which means delaying results). ELISA techniques ( VWF: CB , VWF: FVIIIB ) known to have drawbacks, including cost, sample collection requirements for proper control, and the complexity of multiple steps involved . Multimer analysis is technically complex, labor-intensive.

16. A study was conducted at our thrombosis and hemostasis laboratory at Assiut university hospital including a number of VWD patients, through it we learned a few things…

17. 1- Applying ISTH-BAT scoring system for VWD patients . 2 - Using rotational thermoelectrometry (ROTEM-INTEM) IN VWD patient’s assessment. 3 - Difficulties in diagnosing severe cases of VWD.

18. 1- Applying ISTH-BAT scoring system for VWD patients.

19. What is the ISTH-BAT? It’s a questionnaire form comprises 14 categories for assessing bleeding symptoms retrospectively. It has been shown that a high bleeding score is associated with the presence of an inherited bleeding disorder. Normal range of BS is 0-3 for adult males, 0-5 for adult females and 0-2 in children.

20. ASH-ISTH guidelines states that:- For patients with a low probability of VWD, BAT is recommended as an initial screening tool to identify which patients required specific blood testing over non-standardized clinical assessment. Specific blood testing for VWD refers to VWF antigen , platelet-dependent VWF activity, and FVIII coagulant activity assay.

21. Total ISTH-BAT score in types and subtypes of VWD in our study

22. Cutoff of ISTH-BAT score in VWD Comparing patients to controls showed a cut-off value of >1 for the total BAT score has a high accuracy of 95.5 %, with high sensitivity of 97.1% and specificity of 94.1% , positive predictive value of 94.4%, and negative predictive value of 97.0%. The area under the curve (AUC) is 0.982 , indicating excellent discriminatory power of predicting bleeding disorder in general and as a good screening tool for VWD.

23. 2- Using rotational thermoelectrometry (ROTEM-INTEM) IN VWD patient’s assessment

24. The use of viscoelastic hemostatic assays, including rotational thromboelastometry (ROTEM) and thromboelastography (TEG) provides information on the global hemostatic process from clot initiation, clot strength, all the way to clot lysis  under low-shear conditions. They have been used to assess coagulation in a variety of clinical settings and subpopulations, including trauma, cardiac surgery, and obstetrics. However, their effectiveness and accuracy in diagnosing bleeding disorders like VWD is still a subject of research and discussion.

25. ROTEM-INTEM graph for one of our patients

26. Correlation between ROTEM parameters (CT, MCF) and other laboratory variables

27. There is a significant difference in CT across VWD types, Sever type 1/type 3 group had the most prolonged CT ( 224.39±60.45). On pairwise comparison showed significant differences between type 2 vs. Sever type 1/type 3 group (P value=0.001), and type 1 vs. Sever type 1 vs. type 3 (P value=0.004). Additionally, in VWD subtypes, there was a significant difference in CT, with subtype 2A/2B having a mean CT of 177.14±25.08, subtype 2N a mean of 182.50±14.84, and subtype 2M a mean of 142.25±22.20. Specifically, significant differences were observed between subtype 2A/2B vs. 2M (P value=0.022), and subtype 2N vs. 2M (P value=0.050). ROTEM results in types and subtypes of VWD

28. Regression analysis revealed that a one-second prolongation in CT is significantly associated with a decrease in VWF :Ag by 0.31% and a decrease in FVIII by 0.482% . The explained variances (R²) for these relationships were 20.0% and 26.6% respectively. Regression Analysis

29. Clotting time for prediction of VWD severity

30. 3- Difficulties in diagnosing severe cases of VWD.

31. Controversy about type 3 VWD diagnosis The ASH ISTH guidelines lack a specific cutoff value to diagnose type 3 VWD , type 3 is defined as a virtual absence of the VWF protein with associated very low FVIII levels ( James et al., 2021 ). Different researchers proposed different cutoff values for diagnosing type 3 as Abdulsalam study reported that diagnosis of type 3 VWD in patients with bleeding requires finding a VWF:Ag and/or VWF:RiCof <0.03  iu /mL, no further testing is usually necessary ( Abdulsalam et al., 2019 ). While Sadler study reported that in most cases, VWF:RCo , VWF:CB and VWF:Ag are < 5 IU dL−1 and FVIII levels are < 10 IU dL−1 ( Sadler et al., 2006a ).

32. Controversy about type 3 VWD diagnosis Some researchers proposed a group of patients called (Severe VWD). This group includes patients of type 3, some patients with severe type 1, 2 A and type 2B VWD. The cutoff for this group was VWF Ag less than 10 % (< 10 %) ( Leebeek and Atiq, 2019 ).

33. In our lab Sysmex CS2500 instrument uses a two-curve system to measure the levels of both VWF Ag and Ac. The medium curve and has a low detection limit of 15 % for VWF Ac and 10 % for VWF Ag, the Low curve has a low detection limit of 4 % for VWF Ac and 2 % for VWF Ag. Any sample result with those numbers is in fact representing a level less than 4 % and 2 %.Due to the unavailability of any method that can detect lower levels of VWF in our laboratory, we opted to consider any VWF levels that are below these values “ severe type 1 vs type 3 VWD”.

34. VWF assay on medium curve

35. VWF assay on low curve

36. Take Home message!! 1- ISTH-BAT questionnaire is a useful screening tool for VWD , as it can quantify bleeding symptoms and assess the severity and may help consequently in predicting VWD type, and it should be used by physicians to help predict the presence of VWD in constrained settings .

37. Take Home message!! 2- We suggest using ROTEM-CT as useful tool for predicting VWD severity and classifying types as a quick, patient side available test when urgent care is needed . Certainly, results interpretation in the context of other diagnostic tools and ISTH-BAT will improve its value in VWD assessment.

38. Thanks!