Summary
A large number of different collagen preparations [n = 21] have been assessed for
their ability to both detect von Willebrands Disease (VWD), and discriminate different
VWD subtypes. Collagen preparations were tested at a range of concentrations and included:
Type I, III and IV, and various mixtures of these, as aqueous supplied preparations
and/or reconstituted from bulk lyophilised stock. Tissue sources for collagens ranged
from human placenta to calf skin to equine tendon. Three of the collagen preparations
tested did not support von Willebrand factor (VWF) binding in an ELISA process (therefore
unable to detect VWD). The ability of the remaining preparations to detect VWF was
variable, as was their ability to discriminate VWD subtypes. Detection of VWF and
discrimination of VWD subtypes was not mutually inclusive. Thus, some collagen preparations
provided excellent detection systems for VWF, but comparatively poorer discrimination
of Type 2 VWD, while others provided good to acceptable detection and discrimination.
Subtype discrimination was also dependent on the collagen concentration, and some
batch to batch variation was evident with some preparations (particularly Type I collagens).
Overall, best discrimination was typically achieved with Type I/III collagen mixtures,
or Type III collagen preparations (where effectiveness was highly dependent on concentration).
Good discrimination was also achieved with a commercial Type III collagen based VWF:CBA
kit method. Results of the various ‘VWF:CBA assays’ are also compared with those using
the Ristocetin Cofactor (VWF:RCof) assay (by platelet agglutination) and that using
a commercial ‘VWF:RCof-alternative/ activity’ ELISA procedure. These latter methodologies
tended to be less sensitive to VWF-discordance when compared to that detected by the
majority of the VWF:CBA procedures.
Abbreviations: FVIII:C Factor VIII: coagulant (assay); HMW High Molecular Weight [VWF]; PNP Pooled
Normal Plasma; RIPA Ristocetin induced platelet aggregation procedure; VWD von Willebrands
disease; VWF von Willebrand Factor; VWF:Ag von Willebrand Factor Antigen (assay);
VWF: CBA Collagen Binding [Activity] Assay for VWF; VWF:RCof Ristocetin Cofactor Assay
for VWF
Keywords von Willebrand factor - VWF - von Willebrands disease - VWD - collagen binding assay
- collagen - VWF:CBA