VWF and von Willebrand disease (hereditary or acquired): The screening tests used to classify VWD are the VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), factor VIII activity (FVIII:C), and VWF collagen binding (VWF:CB), whereas the confirmatory tests include ristocetin-induced platelet agglutination (RIPA), VWF capacity to bind exogenous FVIII (VWF:FVIIIB), VWF propeptide (VWFpp), and multimeric analysis (MA), which are especially useful to differentiate between the different types of VWD.