von Willebrand disease (VWD) is reportedly the most common inherited bleeding disorder and can also arise as an acquired syndrome (AVWS). These disorders arise 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 protocols for assessment of VWF level by means of VWF antigen (VWF:Ag). These assays identify VWF levels by quantitative assessment of VWF protein by means of immunological assays. The most commonly performed assays for VWF:Ag comprise enzyme-linked immunosorbent assays (ELISA) and latex-enhanced immunoassays (LIA), as described in this chapter.
Keywords: VWD; VWF; VWF:Ag; von Willebrand disease; von Willebrand factor; von Willebrand factor antigen.