Use of objective efficacy criteria for evaluation of von Willebrand factor/factor VIII concentrates.

von Willebrand disease (VWD) is the most common inherited coagulation disorder and is typically treated by restoring the deficient von Willebrand factor (VWF) with exogenous VWF or by stimulating release of endogenous VWF with desmopressin. Assessment of treatment efficacy is complex because there are no standardized criteria or consistent methodology in their application. The traditionally used four-point Likert scale, with criteria that are not clearly defined or easily quantifiable, relies on a subjective rating of efficacy, and is thus open to observer bias. This article presents a novel approach to assessing efficacy of VWF replacement therapy. A new objective scoring system for assessment of the treatment efficacy of bleeding episodes (objective set of criteria for evaluation of treatment efficacy in VWD) was developed to assess a new-generation human plasma-derived VWF/coagulation factor VIII concentrate (Wilate). This manuscript analyzes the results obtained using a traditional subjective scoring system for hemostatic efficacy and compares them with results obtained when a specifically developed set of stringent objective and well defined success/failure criteria are applied in a clinical trial setting. This new assessment tool provided improved objectification of the subjective judgments obtained from the recipients of the replacement therapy. A validated tool like this could ultimately be applied to clinical comparability studies for the multiplicity of new generation replacement products, as healthcare providers, regulatory agencies, and manufacturers must now consider the additional benefits conveyed by treatment modalities, such as treatment duration, alternative dosing regimens, and treatment frequency. The objective criteria appear to be more robust and present a more conservative assessment of treatment efficacy while avoiding observer and recipient bias and inconsistencies. This new approach may be a more suitable alternative for hemostatic assessment of coagulation products in VWD patients than the currently used subjective methods.