The severity of bleeding in VWD is strongly related to the degree of reduction in VWF activity and also related to the reduction in coagulation factor VIII in the more severe subtypes of VWD.
The diagnosis of VWD often is complicated, and it may be difficult both to distinguish persons with mild forms of VWD from the normal population, and also to identify the specific subtype of VWD. Diagnostic criteria have been proposed by the ISTH.
Treatment of VWD includes a choice between a drug that helps release von Willebrand factor into the bloodstream (desmopressin/DDAVP) and VWF concentrates that are purified from healthy blood donors. Since the response varies to DDAVP, responders must be identified by testing.
In order to avoid diagnosing healthy persons as having VWD, the NHC recommends that the diagnosis of VWD should in general be reserved for individuals with repeated VWF:RCo levels below about 0.35 kIU/L. Individuals with marginally low VWF:RCo level (about 0.36-0.50 kIU/L), despite having excessive bleeding, should not in general be labelled as VWD but simply as having increased risk of bleeding.
Nordic Hemophila Council Guidelines 2008: Von Willebrand disease - Guidelines