Desmopressin therapy to assist the functional identification and characterisation of von Willebrand disease: Differential utility from combining two (VWF:CB and VWF:RCo) von Willebrand factor activity assays?

The Role of the von Willebrand Factor Collagen-Binding Assay (VWF:CB) in the Diagnosis and Treatment of von Willebrand Disease (VWD) and Way Beyond: A Comprehensive 36-Year History

The von Willebrand factor (VWF) collagen binding (VWF:CB) assay was first reported for use in von Willebrand diagnostics in 1986, by Brown and Bosak. Since then, the VWF:CB has continued to be used to help diagnose von Willebrand disease (VWD) (correctly) and also to help assign the correct subtype, as well as to assist in the monitoring of VWD therapy, especially desmopressin (DDAVP). However, it is important to recognize that the specific value of any VWF:CB is predicated on the use of an optimized VWF:CB, and that not all VWF:CB assays are so optimized. There are some good commercial assays available, but there are also some "not-so-good" commercial assays available, and these may continue to give the VWF:CB "a bad reputation." In addition to VWD diagnosis and management, the VWF:CB found purpose in a variety of other applications, from assessing ADAMTS13 activity, to investigation into acquired von Willebrand syndrome (especially as associated with use of mechanical circulatory support or cardiac assist devices), to assessment of VWF activity in disease states in where an excess of high-molecular-weight VWF may accumulate, and lead to increased (micro)thrombosis risk (e.g., coronavirus disease 2019, thrombotic thrombocytopenic purpura). The VWF:CB turns 37 in 2023. This review is a celebration of the utility of the VWF:CB over this nearly 40-year history.

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

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.

Utility of the von Willebrand factor collagen binding assay in the diagnosis of von Willebrand disease

von Willebrand Disease (VWD) is the most common inherited bleeding disorder and also arises as an acquired defect (AVWS). VWD and AVWS are due to quantitative deficiencies and/or qualitative defects in von Willebrand factor (VWF), an adhesive plasma protein with multiple activities. Diagnosis of VWD is problematic, being subject to overdiagnosis, underdiagnosis, and misdiagnosis. This is largely due to limitations in current test procedures and an over-reliance on these imperfect test systems for clinical diagnosis. VWF essentially acts to assist in the formation of a platelet thrombus to stop blood loss from sites of injury, achieving this by binding to platelets (primarily through the glycoprotein Ib receptor), binding to subendothelial matrix components (primarily collagen), and binding to factor VIII (FVIII), thus protecting FVIII from degradation and enabling its delivery to sites of vascular injury. VWD is classified into six separate types, which may each be differentially managed therapeutically, and this underscores the importance of a correct diagnosis. The current report concisely reviews the utility of a relatively underutilised assay, the VWF collagen binding assay (VWF:CB), in facilitating the correct diagnosis and typing of VWD. In particular, if laboratories do not utilise the VWF:CB, then (i) type 2M VWD will continue to be missed, and/or misdiagnosed as types 2A or 1 VWD, and (ii) types 2A, 2B and PT-VWD will continue to be missed, or else be misdiagnosed as type 1 VWD or ITP. Am. J. Hematol. 92:114-118, 2017. © 2016 Wiley Periodicals, Inc.

Towards personalised therapy for von Willebrand disease: a future role for recombinant products

von Willebrand disease (VWD) is reportedly the most common bleeding disorder and is caused by deficiencies and/or defects in the adhesive plasma protein von Willebrand factor (VWF). Functionally, normal VWF prevents bleeding by promoting both primary and secondary haemostasis. In respect to primary haemostasis, VWF binds to both platelets and sub-endothelial matrix components, especially collagen, to anchor platelets to damaged vascular tissue and promote thrombus formation. VWF also stabilises and protects factor VIII in the circulation, delivering FVIII to the site of injury, which then facilitates secondary haemostasis and fibrin formation/thrombus stabilisation. As a result of this, patients with VWD suffer a bleeding diathesis reflective of a primary defect caused by defective/deficient VWF, which in some patients is compounded by a reduction in FVIII. Management of VWD, therefore, chiefly entails replacement of VWF, and sometimes also FVIII, to protect against bleeding. The current report principally focuses on the future potential for "personalised" management of VWD, given the emerging options in recombinant therapies. Recombinant VWF has been developed and is undergoing clinical trials, and this promising therapy may soon change the way in which VWD is managed. In particular, we can envisage a personalised treatment approach using recombinant VWF, with or without recombinant FVIII, depending on the type of VWD, the extent of deficiencies, and the period and duration of treatment.

Evaluation of a rapid von Willebrand factor activity latex immuno assay for monitoring of patients with von Willebrand disease (VWD) receiving DDAVP or VWF replacement therapy

Haemostatic management of surgery in patients with von Willebrand disease (VWD) includes DDAVP or von Willebrand factor (VWF)-containing concentrates. Although the recommendations are for monitoring by VWF activity assays, it is quite common for clinicians to use factor VIII due usually to longer turnaround times required for VWF ristocetin cofactor assay (VWF:RCo) measurements. The aim of this study was to evaluate use of the rapid HaemosIL VWF activity (VWF:Act) latex immuno assay (LIA) on an automated coagulometer (ACL TOP(™) 700; Instrumentation Laboratory, Bedford, MA, USA) compared to platelet-based VWF:RCo assays in this setting. One hundred and sixty-seven plasma samples from 42 patients [Type 1 (n = 22), Type 2A (n = 2), Type 2B (n = 3), Type 2M (n = 10), Type 3 (n = 3)] and acquired von Willebrand syndrome (n = 2) with VWD treated with DDAVP or VWF-containing concentrates were included in the study. Method comparison and method bias were evaluated by Bland-Altman analysis (BA) and Passing and Bablok regression modelling respectively. BA of baseline samples (n = 39) showed a mean difference of -3.0 (±1.96 SD -25.2 to +19.4). Post (treatment) samples (n = 120) were separated into two groups. Group 1 contained samples with VWF:RCo levels 10 to ≤175 IU dL(-1) (n = 97) and group 2, samples with VWF:RCo levels >175 IU dL(-1) (n = 23). BA of group 1 postsamples showed a mean difference of +3.4 (±1.96 SD -44.6 to +51.5), and the BA of Group 2 samples was -23.9 (±1.96 SD -136.1 to +88.3). In conclusion, use of HaemosIL VWF:Act LIA test on an automated coagulometer is a reproducible and rapid assay that can be used as an alternative test for monitoring VWF replacement therapy, facilitating dose adjustments on a real-time basis.

Perils, problems, and progress in laboratory diagnosis of von Willebrand disease

Diagnosis of von Willebrand disease (VWD) merits consideration of personal and family history of bleeding symptoms along with confirmatory laboratory testing. As the latter yields quantifiable results, overreliance on a laboratory diagnosis may occur. However, existing tests for VWD contain potential sources for error. Both intrinsic and extrinsic factors affecting these assays can contribute to either falsely normal or falsely abnormal results. This article will discuss the present available assays as well as new developments in diagnostic testing. A clear understanding of the limitations of VWD testing is helpful for ensuring the correct diagnosis of affected patients.

Differential sensitivity of von Willebrand factor (VWF) 'activity' assays to large and small VWF molecular weight forms: a cross-laboratory study comparing ristocetin cofactor, collagen-binding and mAb-based assays

BACKGROUND

von Willebrand disease (VWD), the most common inherited bleeding disorder, is caused by deficiencies and/or defects in von Willebrand factor (VWF). An effective diagnostic and VWD typing strategy requires plasma testing for factor VIII, and VWF antigen plus one or more VWF 'activity' assays. VWF activity is classically assessed by using VWF ristocetin cofactor activity (VWF:RCo), although VWF collagen-binding (VWF:CB) and VWF mAb-based (VWF activity [VWF:Act]) assays are used by some laboratories.

OBJECTIVE

To perform a cross-laboratory study to specifically evaluate these three VWF activity assays for comparative sensitivity to loss of high molecular weight (HMW) VWF, representing the form of VWF that is most functionally active and that is absent in some types of VWD, namely 2A and 2B.

METHODS

A set of eight samples, including six selectively representing stepwise reduction in HMW VWF, were tested by 51 different laboratories using a variety of assays.

RESULTS

The combined data showed that the VWF:CB and VWF:RCo assays had higher sensitivity to the loss of HMW VWF than did the VWF:Act assay. Moreover, within-method analysis identified better HMW VWF sensitivity of some VWF:CB assays than of others, with all VWF:CB assays still showing better sensitivity than the VWF:Act assay. Differences were also identified between VWF:RCo methodologies on the basis of either platelet aggregometry or as performed on automated analyzers.

CONCLUSIONS

We believe that these results have significant clinical implications for the diagnosis of VWD and monitoring of its therapy, as well as for the future diagnosis and therapy monitoring of thrombotic thrombocytopenic purpura.