Pathophysiological mechanisms in patients with low VWF compared with type 1 VWD subgroups. FVIII:C/VWF:Ag and VWFpp/VWF:Ag ratios were assessed in patients with low VWF and type 1 VWD to assess underlying pathophysiology. (A) Significantly increased plasma FVIII:C/VWF:Ag ratios suggesting marked reductions in VWF synthesis/secretion were observed in the WiN persistent <30 IU/dL subgroup. In contrast, FVIII:C/VWF:Ag ratios were the same in LoVIC and WiN-normalized patients. (B) Similarly, significantly increased plasma VWFpp/VWF:Ag ratios suggesting markedly enhanced VWF clearance were also observed in the WiN persistent <30 IU/dL subgroup. Again, VWFpp/VWF:Ag ratios were not significantly different between LoVIC and WiN-normalized patients. Ns, not significant.