VWF and von Willebrand disease 1: Platelet VWF is rarely measured, but it is a good tool for exploring VWF synthesis because—unlike plasma VWF—it is uninfluenced by environmental factors, especially aging and morbidities; in our experience, platelet VWF does not change significantly with age, whereas circulating VWF does, especially in type 1 VWD patients with mild VWF defects (unpublished data).