Enhanced clearance plays an important role in the pathogenesis of low VWF. (A) VWF:Ag fall-off (decrease in VWF:Ag from T+1 to T+4 hours after desmopressin infusion, as a percentage of T+1) is illustrated on the y-axis. The red dotted line and shaded area illustrate the ASH/ISTH/NHF/WFH guideline7 threshold of >30% for enhanced clearance. (B) Plasma VWF:Ag levels at 1 hour and 4 hours after desmopressin treatment in patients with low VWF with FC compared with patients with low VWF with NC rates. (C) Patients with low VWF with FC had a significantly greater increment in plasma VWF:Ag levels at 1 hour after desmopressin (median, 3.84-fold vs 2.89-fold; P < .0001). The increment is expressed as fold change (T+1/T0). Similarly, patients with low VWF with FC demonstrated significantly greater increments in plasma VWF:RCo (D) (median, 4.66-fold vs 3.60-fold; P < .0001) and plasma FVIII:C levels (E) (median, 3.40-fold vs 2.81-fold; P < .01) at 1 hour after desmopressin infusion. (F-H) Conversely, patients with low VWF with FC demonstrated greater fall-offs in plasma VWF:Ag, VWF:RCo, and FVIII:C levels between 1 hour and 4 hours after desmopressin. All fall-off values are expressed as fold change between the 1-hour and 4-hour time points. (I-J) In patients with low VWF, fall-off rates in plasma VWF:Ag levels after desmopressin treatment correlated significantly with fall-off rates in both VWF:RCo and FVIII:C (Pearson’s r), consistent with faster clearance of the VWF-FVIII complex from the circulation. Median values are illustrated by black lines. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. ns, not significant.
