Summary
This study reports on the evaluation of seven commercial von Wille-brand factor (VWF)
collagen binding (VWF:CB) assays to potentially assist the discrimination of types
1 and 2 von Willebrand disease (VWD). Samples from 25 patients with type 1 VWD, of
varying severity, were co-tested with 16 samples from patients with types 2A or 2B
VWD, plus various control samples, using each commercial VWF:CB assay assessed against
our standard (reference) in-house VWF:CB assay, as well as our in-house VWF antigen
(VWF:Ag) and ristocetin cofactor (VWF:RCo) assays. Commercial VWF:CB assays varied
in their ability to discriminate types 1 and 2A/2B VWD. The optimal VWF:CB/VWF:Ag
ratio at which optimal discrimination occurred also differed between assays, with
some improvements observed with some (but not all) as-says following a harmonisation
process that aimed to correct for different calibrator effects. Assay variability
also compromised assay utility in some test occasions. Future standardisation and
improvements in some commercial VWF:CB assays are needed before the VWF:CB assay can
be more fully and globally utilised for discrimination of VWD types in diagnostic
laboratories.
Keywords
von Willebrand factor - VWF - collagen binding - von Willebrand disease - VWD - diagnosis