Laboratory Testing for von Willebrand Factor: Factor VIII Binding (for 2N VWD).

Von Willebrand disease (VWD) is reportedly the most common inherited bleeding disorder and can also arise as an acquired syndrome (AVWS). These disorders develop due to defects and/or deficiency of the plasma protein von Willebrand factor (VWF). Laboratory testing for the VWF-related disorders requires assessment of both VWF level and VWF activity, the latter requiring multiple assays because of the many functions carried out by VWF to help prevent bleeding. The current paper describes a protocol for assessment of VWF activity by means of VWF: factor VIII binding (VWF:FVIIIB). Such assays identify VWF activity by quantitative assessment of VWF protein adhesion to FVIII, which is the activity lost in type 2N VWD. This assay is therefore a critical assay for identification or exclusion of 2N VWD. The most commonly performed assays for VWF:FVIIIB comprise enzyme-linked immunosorbent assays (ELISA), and such an assay is described in this chapter.