scope:

This guideline provides selected methods for measuring vWFAg and R:CoF. Specimen requirements, reagents and materials, preparation of reference curves, establishment of reference intervals, result reporting, quality control, and common sources of error are addressed. A brief description of von Willebrand Disease (vWD) and its various subtypes is included, as well as references to more comprehensive reviews of this commonly inherited and rarely acquired bleeding disorder.

The method described for measuring vWFAg is an ELISA technique. The method described for measuring R:CoF utilizes a turbidimetric platelet aggregometer to measure changes in light transmission and the extent of agglutination of formalin-fixed platelets by ristocetin in the presence of test plasma. The R:CoF assay described here must be distinguished from the ristocetin-induced platelet agglutination assay (RIPA), which is performed in freshly prepared, citrated, platelet-rich, test plasma using different concentrations of ristocetin to distinguish between different types of vWD.