Should von Willebrand factor testing be repeated before excluding the diagnosis of von Willebrand disease?
Alfonso Iorio, MD, PhD: Yes. A very good point. It is a functional test and it is very variable. Von Willebrand factor is an acute-phase reactant, so it can be falsely increased for exercise, or if, for example, the lady rushed to the laboratory, ran upstairs. It has been shown to increase significantly with physical exercise. So it is a good norm to repeat it, making sure on the repeat that the patient calms down for 15 minutes before being tested.