Detection of von Willebrand disorder and identification of qualitative vonWillebrand factor defects - Direct comparison of commercial ELISA-based von Willebrand factor activity options

Two vonWillebrand factor (nu WF): collagen binding (activity) assay (CBA) k it methods are commercially available. A monoclonal antibody (MAB)-based en zyme-linked immunosorbent assay (ELISA) system reported to correlate with a standard nu WF:ristocetin cofactor (RCof) assay is also commercially avail able. It is marketed as a nu WF:Activity assay and is available in 2 assay version formats. In the present study, these 4 nu WF-activity options were compared directly with in-house nu WF:CBA ELISAs for their ability to detec t von Willebrand disease (nu WD) and identify qualitative nu WF defects. Th e 2 MAB-based systems detected nu WD but could not specifically identify qu alitative nu WF defects, although the recently modified Mark II kit was mor e effective for the latter compared with the original Mark I kit. All nu WF :CBA methods, including in-house and commercial, also effectively detected nu WD but differed in their ability to identify, qualitative nu WF defects. Effectiveness was highest using the in-house reference nu WF:CBA (using a type I/III collagen mix product from equine tendon), the Gradipore nu WF:CB A (also uses equine tendon-derived collagen), or the in-house nu WF:CBA met hods using type III human collagen at a relatively low concentration (1 or 3 mug/mL, without covalent linkage). The IMMUNO nu WF:CBA seemed to be the least effective among the nu WF:CBA methods for detection of qualitative nu WF defects.