We performed a retrospective audit of cross-laboratory testing of
desmopressin and factor concentrate
therapy to assess the potential utility of supplementary testing using the PFA-100 with functional
von Willebrand factor (VWF) activity testing. Data were evaluated for a large number of patients with
von Willebrand disease of type 1, type 2A or type 2M, as well as a comparative subset of individuals with
haemophilia or carriers of
haemophilia. Laboratory testing comprised pre and postdesmopressin, or pre and postconcentrate, evaluation of
factor VIII, VWF
antigen (VWF:Ag) and VWF
ristocetin cofactor activity as traditionally performed, supplemented with
collagen-binding (VWF:CB) testing and PFA-100 closure times. In brief, both
therapies tended to normalize VWF test parameters and closure times in individuals with
type 1 von Willebrand disease, with the level of correction in closure times related to the level of normalization of VWF, particularly the VWF:CB. However, although occasional correction of closure times was observed in patients with type 2A or
type 2M von Willebrand disease, these did not in general normalize PFA-100 closure times either with
desmopressin or factor concentrate
therapy. In these patients, improvement in closure times was more likely in those in whom VWF:CB values normalized or when VWF:CB/VWF:Ag ratios normalized. This study confirms that there is a strong relationship between the presenting levels of plasma VWF and PFA-100 closure times, and that the supplementary combination of PFA-100 and VWF:CB testing might provide added clinical utility to current broadly applied testing strategies limited primarily to VWF:Ag, VWF
ristocetin cofactor and
factor VIII:
coagulant. Future prospective investigations are warranted to validate these relationships and to investigate their therapeutic implications.