DDAVP Challenges in 170 Children With von Willebrand Disease: Response Classification Varies According to Criteria Used

INTRODUCTION: Individuals diagnosed with types 1/1C/2A/2M von Willebrand disease (VWD) typically undergo a desmopressin (DDAVP) challenge to assess therapeutic benefit. This involves measuring von Willebrand factor antigen (VWF:Ag), activity (VWF:Act; VWF:RCo/VWF:GPIbM/VWF:Ab), and coagulant factor VIII (FVIII:C) levels 0 (pre), 1, and 4-h post-DDAVP administration. Diverse systems exist to classify DDAVP response (complete (CR), partial (PR), and non-responders (NR)). These have not been compared in a paediatric population. AIM: To compare DDAVP response classification systems in children with VWD and to explore predictors of DDAVP response: VWD subtype, age, blood group, and baseline VWF:Act. METHODS: In this retrospective single-centre study, subjects were included if they had type 1/1C/2A/2M VWD and underwent a DDAVP challenge. DDAVP response was classified according to two recent classification systems: Castaman (2020) and Connell et al. (2021). RESULTS: 170 subjects were included (124, 12, 13, and 21 with types 1/1C/2A/2M VWD, respectively; 84 male, 86 female). Median age at DDAVP challenge was 7.1 years [IQR 4.8-10.8]. CR rate varied from 59% (Connell et al.) to 81% (Castaman). Those with type 1 had higher rates of CR compared to types 1C/2A/2M VWD. Age and blood group did not predict DDAVP response. 90%-98% of those with baseline VWF:Act ≥0.30 had a CR. CONCLUSION: Inconsistent DDAVP response criteria between classification systems may lead to inconsistent use of DDAVP. As the Castaman system does not require a >2-fold increase in VWF:Act, it may be more realistic in children who may already have a stress-induced increase in levels at time 0-h of the challenge.