Pathogenic mechanisms in patients with low VWF subgroups and type 2A/B/M VWD. (A) The FVIII:C/VWF:Ag ratio (a marker of VWF synthesis/secretion; n = 124, n = 25, and n = 225, respectively) and (B) the VWFpp/VWF:Ag ratio (a marker of VWF clearance) were compared among patients with low VWF with VWF:GPIbM/VWF:Ag ratios ≥0.7 (n = 60), those with VWF:GPIbM/VWF:Ag ratios <0.7 (n = 15), and those with type 2A/B/M VWD (n = 224). The P values were determined using independent t tests. (C) The VWF:Act/VWF:Ag ratio before and after desmopressin in patients with low VWF with VWF:GPIbM/VWF:Ag ratios of ≥0.7 (n = 74) or <0.7 (n = 16) and those with type 2A/B/M VWD (n = 61). The P values were determined using independent t tests.