Collagen Binding Provides a Sensitive Screen for Variant von Willebrand Disease

Abstract

Background Von Willebrand factor (VWF) is a multimeric protein that binds platelets and collagen, facilitating hemostasis at sites of vessel injury. Measurement of VWF multimer distribution is critical for diagnosis of variant von Willebrand disease (VWD), particularly types 2A and 2B, but the typical measurement by gel electrophoresis is technically difficult and time consuming. A comparison of VWF collagen binding (VWF:CB) and VWF multimer distribution was performed to evaluate the utility of VWF:CB as a diagnostic test. Methods Participants were enrolled in the Zimmerman Program for the Molecular and Clinical Biology of VWD. VWF:CB was analyzed with type III collagen and multimer distribution by agarose gel electrophoresis. The study population included 146 healthy controls, 351 individuals with type 1 VWD, and 77 with type 2 VWD. Differences between normal and abnormal multimer groups were assessed with Mann-Whitney tests. Results The mean VWF:CB/VWF antigen ratio was 1.10 for individuals with normal multimer distribution and 0.51 for those with abnormal multimer distribution (P<0.001). Sensitivity of VWF:CB for multimer abnormalities was 100% for healthy controls, 99% for type 1, and 100% for type 2A and type 2B VWD using a VWF:CB/VWF antigen cutoff ratio of 0.6, and decreased to 99% for all with a ratio of 0.7. With the exception of individuals with novel or unclassified mutations, the VWF:CB was able to correctly categorize participants with variant VWD. Conclusions These findings suggest VWF:CB may substitute for multimer distribution in initial VWD testing, although further studies are needed to validate its clinical utility.

An update on type 2B von Willebrand disease

“…VWF multimers assays which are critical to differentiation of different types of VWD are resource intensive and only available at a limited number of reference labs. Recent studies show promise that VWF collagen-binding assay/VWF antigen ratios may be able to substitute for multimers analysis in the diagnosis of VWD [140]. Finally, as highlighted in the NHLBI clinical guidelines, it is of paramount importance to train and recruit basic and clinical researchers as well as clinicians with expertise in hemostasis and non-malignant hematology to address the current shortages of physicians/scientists in these fields.…”

Standardization and comparison of nonautomated assays to measure the collagen binding activity of von Willebrand factor

“…Regardless the limited number of patients with conclusive molecular diagnosis of VWD, the VWF:CB/VWF:Ag ratio using Technozym vWF:CBA ELISA and VWF:CB‐IH results could differentiate 2A and 2M VWD as discussed in previous studies . Surprisingly, the VWF:CB/VWF:Ag ratio using VWF:CB‐FC results could not discriminate these 2 subtypes of VWD.…”

Microfluidic technology as an emerging clinical tool to evaluate thrombosis and hemostasis

“…As compared to the static nature of current collagen binding assays [40], microfluidic assays may allow for the characterization of abnormalities in VWF-collagen binding under physiologic shear stresses and can further elucidate novel pathology in this relationship. Future microfluidic-based approaches to VWD, especially those with type 1 disease, could involve comparison of individual patients’ aggregation patterns to those of existing cohorts, once established, to help predict clinical bleeding.…”