Diagnosis of von Willebrand disease (VWD) and differentiation of VWD subtype (in conjunction with von Willebrand factor ristocetin cofactor activity and factor VIII coagulant activity)Differentiation of VWD from hemophilia A (in conjunction with factor VIII coagulant assay) VWF is an acute-phase reactant and may be elevated above baseline in association with a variety of conditions including inflammation, stress, exercise, liver disease, pregnancy or estrogen therapy. Baseline VWF levels also increase with aging. These conditions may obscure diagnosis of the milder forms of von Willebrand disease (VWD).