How we diagnose 2M von Willebrand disease (VWD): Use of a strategic algorithmic approach to distinguish 2M VWD from other VWD types

Abstract

Introduction von Willebrand disease (VWD) is the most common inherited bleeding disorder and caused by an absence, deficiency or defect in von Willebrand factor (VWF). VWD is currently classified into six different types: 1, 2A, 2B, 2N, 2M, 3. Notably, 2M VWD is more often misdiagnosed as 2A or type 1 VWD than properly identified as 2M VWD. Aim To describe an algorithmic approach to better ensure appropriate identification of 2M VWD, and reduce its misdiagnosis, as supported by sequential laboratory testing. Methods Comparative assessment of types 1, 2A, 2B and 2M VWD using various laboratory tests, including VWF antigen and several VWF activity assays, plus DDAVP challenge data, ristocetin‐induced platelet agglutination (RIPA) data, multimer analysis and genetic testing. Results Types 1, 2A, 2B and 2M VWD give characteristic test patterns that can provisionally classify patients into particular VWD types. Notably, type 1 VWD shows low levels of VWF, but VWF functional concordance (VWF activity/Ag ratios >0.6), with both baseline assessment and post‐DDAVP. Types 2A, 2B and 2M VWD show VWF functional discordance (low VWF activity/Ag ratio(s)) dependent on the defect, but type 2M separates from 2A/2B VWD based on specific test patterns, especially with collagen binding vs glycoprotein Ib binding assays. RIPA identifies 2B VWD. Multimers separate 2M from 2A/2B. Conclusion We provide strategies to improve correct diagnosis of VWD, especially focussed on 2M VWD, and which can be used by most diagnostic haemostasis laboratories, reserving genetic analysis (if required) for confirmation.

Commentary on the ASH ISTH NHF WFH 2021 guidelines on the diagnosis of VWD: reflections based on recent contemporary test data

“…For this, I would largely highlight some recent work that has been published. 6,7,[9][10][11][12][13] First, in our most recent external quality assessment (EQA) publication, 9 highlighting "VWD diagnostic errors" as linked to test types/test panels, we found, as detailed in Table 1: (a) VWF:RCo showed highest assay variability and poorest quantification limit among all platelet-dependent VWF activity assays; (b) VWF:GPIbR performed by chemiluminescence immunoassay (CLIA) was the least variable (with lowest quantification limit) platelet-dependent VWF activity assay, followed in turn by VWF:GPIbR by latex immunoassay (LIA), VWF:GPIbM (LIA), and VWF:RCo (Figure 1A); (c) CLIA methodology was the least variable method overall (all available assays) (Figure 1A); (d) for associated diagnostic errors of type 1 ('quantitative' VWF deficiency) vs type 2A/2B (high molecular weight [HMW] VWF deficiency) samples, the most problematic platelet-dependent VWF activity assay was VWF:RCo, followed by VWF:GPIbM; comparatively, VWF:GPIbR and VWF:CB were associated with few errors; (f) error rates associated with a 'standard' 3-test panel (i.e., as per the guidelines 1 -FVIII:C, VWF:Ag, platelet-dependent VWF activity assay) were twice that of a 4-test panel including the VWF:CB; (g) no single 'universal' cut-off value (e.g., 0.5 or 0.7) for activity/Ag was sufficiently robust to effectively identify/exclude type 2A/B VWD; indeed, ideal cut-off values are method 'specific' (Figure 1B), but should a universal cut-off be required, perhaps 0.6, in line with recommendations of the UK Haemophilia Doctors organization 4 could be favored (also see Supplementary Figure 1); (h) best VWD type discrimination was achieved using CLIA methods (i.e., GPIbR/Ag or CB/Ag), followed by GPIbR/Ag (LIA); other methods, including RCo/Ag and GPIbM/Ag showed substantial ratio overlap between type 1 vs 2A/2B VWD (Figure 1B). In summary, the composite of this EQA data would favor CLIA methodology over all other methodologies, and for platelet-binding activity assays would favor VWF:GPIbR over both VWF:GPIbM and VWF:RCo.…”

“…Third, such studies cannot address the issue of polymorphisms affecting ristocetin binding and influencing the panel’s recommendation of VWF:GPIbM over VWF:GPIbR; however, although apparently common in Black populations, homozygous changes are uncommon in White populations, 8 and my own experience indicates low incidence in my geographic locality of Australia. 12 Indeed, my laboratory has only ever identified a single known case of such a polymorphism causing a false type 2M VWD diagnosis. 12 Therefore, using a VWF:GPIbR assay rather than VWF:GPIbM could be considered appropriate in areas where few Black individuals live, especially given the comparatively favorable findings shown here.…”

“… 12 Indeed, my laboratory has only ever identified a single known case of such a polymorphism causing a false type 2M VWD diagnosis. 12 Therefore, using a VWF:GPIbR assay rather than VWF:GPIbM could be considered appropriate in areas where few Black individuals live, especially given the comparatively favorable findings shown here. Lastly, data are influenced by the assays available to EQA participants, as well as by samples tested.…”

Resolving Differential Diagnostic Problems in von Willebrand Disease, in Fibrinogen Disorders, in Prekallikrein Deficiency and in Hereditary Hemorrhagic Telangiectasia by Next-Generation Sequencing

“…Type 2M is often misdiagnosed as 2A or type 1, moreover, according to the site of mutation it can be associated with a collagen-binding defect (mutations in the A3 domain, or in some cases in the A1 domain), or with a reduced platelet-dependent activity (mutations in the A1 domain) [ 63 ]. Classification of vWD Vicenza (p.Arg1205His) has always been controversial [ 64 ].…”

“Von Willebrand disease type 2M: Correlation between genotype and phenotype”: Comment from Favaloro

“…Although VWF:GPIbR and VWF:GPIbM tend to show test patterns fairly aligned to those of classical VWF:RCo, there are also differences among these three assays. 4 Of additional interest, the most robust assays seem to be those based on chemiluminescence, 4,9 this being true for VWF:Ag, VWF:GPIbR, and VWF:CB, compared with other methodologies (i.e., latex or ELISA based). I therefore urge the authors of the prior JTH paper 1 to provide differential data according to which "VWF:Act" assay was performed (this can be as simple as adding the VWF:Act method used per case to their published supplementary file table) to enable determination of whether such differentials also exist in their data set.…”