von Willebrand disease: proposing definitions for future research

von Willebrand disease (VWD) is a common bleeding disorder, which affects 1 in 100 individuals based on laboratory testing and at least 1 in 1000 individuals based on presence of abnormal bleeding symptoms.1,2 VWD was first described almost 100 years ago, and since the initial report, major advances in both diagnostic testing and treatment options have improved outcomes for patients living with VWD; however, many patients still experience significant complications and barriers to treatment. An underlying problem is the lack of consistent unified definitions. In recent work developing evidence-based guidelines for VWD,3,4 it was noted that studies on VWD often used varying definitions. For example, studies of von Willebrand factor (VWF) concentrates did not have consistent definitions for major bleeding, studies on VWF prophylaxis did not use consistent definitions of what constituted a prophylaxis regimen, and studies on desmopressin did not use consistent definitions of desmopressin responsiveness. In addition, common bleeding conditions, such as heavy menstrual bleeding (HMB) and postpartum hemorrhage are variably defined. Such inconsistencies in describing study regimens and endpoints hinder the ability to compare study outcomes and to advance treatment of patients with VWD. We propose definitions for future use in VWD research to facilitate comparison of treatment options. These definitions are based on the most common usage in the literature and endeavor to encompass the most common situations in VWD. The proposed definitions were derived from existing literature and discussed at the first in-person meetings of the guideline panels. Group members made amendments, and the consensus document was circulated to the group. All authors approved the final document.