title: Establishment and characterization of a new and stable collagen-binding assay for the assessment of von Willebrand factor activity.
abstract: BACKGROUND
  Laboratory diagnosis of von Willebrand disease (VWD) requires determination of both von Willebrand factor (VWF) protein levels and activity. Current VWF activity tests include the ristocetin cofactor assay and the collagen-binding assay (VWF:CB). The goal of this investigation is to characterize a new collagen-binding assay and to determine its effectiveness in identifying VWD.
  
  
  METHODS
  Analytical studies were carried out to characterize the performance of a new VWF:CB ELISA. Additionally, samples from a normal population were tested as were well-characterized type 1 and type 2 VWD samples.
  
  
  RESULTS
  Repeatability and within-laboratory precision studies resulted in coefficients of variation (CVs) of ≤11%. A linear range of 1-354% (0.01-3.54 IU/mL) was determined, along with a limit of detection and a lower limit of quantitation of 1.6% and 4.0% (0.016 and 0.04 IU/mL), respectively. Samples tested from apparently healthy individuals resulted in a normal range of 54-217% (0.54-2.17 IU/mL). Known VWD type 1 and type 2 samples were also analyzed by the ELISA, with 99% of samples having VWF:CB below the normal reference range and an estimated 96% sensitivity and 87% specificity using a VWF collagen-binding/antigen cutoff ratio of 0.50.
  
  
  CONCLUSIONS
  This new VWF:CB ELISA provides an accurate measure of collagen-binding activity that aids in the diagnosis and differentiation of type 1 from type 2 VWD.
authors.affiliation: Precision BioLogic, Dartmouth, NS, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Ni
authors.forename: J
authors.initials: J
authors.lastname: Nesrallah
authors.forename: M
authors.initials: M
authors.lastname: Agnew
authors.forename: F J
authors.initials: FJ
authors.lastname: Geske
authors.forename: E J
authors.initials: EJ
authors.lastname: Favaloro
mesh_terms: D019963:Clinical Chemistry Tests / Q000379:methods*; D003094:Collagen / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D012680:Sensitivity and Specificity; D056725:von Willebrand Disease, Type 1 / Q000175:diagnosis; D056728:von Willebrand Disease, Type 2 / Q000175:diagnosis; D014841:von Willebrand Factor / Q000032:analysis*
chemical_list: D014841:von Willebrand Factor; D003094:Collagen