Evaluation of the PFA-100 (R) system in the diagnosis and therapeutic monitoring of patients with von Willebrand disease

We have evaluated platelet function at high shear with the PFA-100(R) syste m in different subtypes of von Willebrand disease (vWD), before and after t he intravenous infusions of desmopressin or a factar-VIII/von Willebrand fa ctor (vWF) concentrate. Closure times with the PFA-100(R) system were deter mined for both the collagen/ADP and the collagen/epinephrine cartridges in 52 patients with vWD (9 type 1 "platelet normal", 5 type 1 "platelet-discor dant", 8 type 1 "platelet-low", 6 type 2A, 9 type 2B, 6 type 2M Vicenza, 6 type 3 and 3 acquired vWD) and 40 controls. Measurements were repeated 1 an d 4 h after the i. v. infusion of desmopressin (0.3 mu g/Kg) in 26 patients with types i, type 2M Vicenza or type 2A vWD, or of a factorVIII/vWF conce ntrate (Alphanate HT, 60 U/Kg) in 4 patients with type 3 vWD. At all time p oints, vWF plasma levels and the bleeding time (Symplate II) were also dete rmined. Baseline closure times were longer in vWD patients than in controls with both the collagen/ADP and the collagen/epinephrine cartridges. The se nsitivity of the PFA-100(R) system (88% and 87% with the two cartridges) wa s higher than that of the bleeding time (65%). Treatment with desmopressin normalized the closure times in patients with type 1 "platelet-normal" or t ype 2M Vicenza vWD, had no significant effects in patients with type 1 "pla telet-low", type 1 "platelet-discordant" or type 2A vWD. Infusion of a fact orVIII/vWF concentrate in patients with type 3 vWD slightly shortened their prolonged closure times. In general, changes in PFA-100(R) were paralleled by shortenings of the bleeding times and increases in plasma VWF levels. T he PFA-100(R) test reflects vWF-dependent platelet function under high shea r stress and could be useful in the diagnosis and therapeutic monitoring of patients with vWD.