Development of a screening method for vWF multimers, using collagen bead columns

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The platelet retention rate as assessed with collagen bead columns are determined by the change in the number of platelets before and after the passage through collagen bead columns. This method has been previously shown to be a simple and useful method for platelet function at bed side. In this study, we sought to develop new collagen bead columns which are most appropriate for the screening of von Willebrand factors. Using a collagen bead column with the bead diameter of 0.125〜0.2mm, we were able to generate sufficient levels of shear stress, which induces platelet activation related to VWF/collagen interaction, followed by VWF/GPIb interaction. With the use of an injection pump commercially available from ISK Ltd., the flow rate of 1.5ml blood within 40sec made it possible to evaluate platelet activation related to GPIb and GPIIb/IIIa.vWF antigen, vWF multimer size, ristocetin cofactor are all used to evaluate the activity of vWF with slightly different properties. We found in this study that all these factors closely correlate with the platelet retention rate of collagen bead columns. Thus, we suggest that the collagen bead column method can be a good screening method for vWF activity, especially that of vWF multimer size.The cases with which the VWF activity measuement and collagen bead columns detected the possibility of high VWF multimer size, ADAMTS-13 activity was measured, using SDS-PAGE and Western blotting, and also a recently developed ELIZA method. Several cases with high VWFmutlimer size were found to have low ADAMTS-13 activity, again confirming the usefulness of the collagen bead column method for screening for VWFmultimer size, and ADAMTS-13 activity.