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

Two vonWillebrand factor (nu WF): collagen binding (activity) assay (CBA) kit methods are commercially available. A monoclonal antibody (MAB)-based enzyme-linked immunosorbent assay (ELISA) system reported to correlate with a standard nu WF:ristocetin cofactor (RCof) assay is also commercially available. 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 detect von Willebrand disease (nu WD) and identify qualitative nu WF defects. The 2 MAB-based systems detected nu WD but could not specifically identify qualitative nu WF defects, although the recently modified Mark II kit was more 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:CBA (also uses equine tendon-derived collagen), or the in-house nu WF:CBA methods 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.