Evaluation of platelet function with the PFA-100 system in patients with congenital defects of platelet secretion.

The template bleeding time is still the screening test for defects of platelet function, although it is an invasive and poorly reproducible technique. The PFA-100 measures platelet function at high shear. Whole blood is aspirated through a capillary to an aperture of a membrane coated with platelet agonists. The system measures the time required to obtain occlusion of the aperture by a platelet plug (closure time). We measured the closure times in the PFA-100 system and the bleeding time in seven patients with delta-storage pool deficiency, 10 patients with "primary secretion defect" (not due to abnormalities of platelet granules or the arachidonate pathway), and 40 controls. Measurements were repeated I and 4 hours after intravenous infusion of desmopressin in six delta-storage pool deficiency and eight primary secretion defect patients. Baseline bleeding time and closure times with the collagen/epinephrine cartridge were longer in delta-storage pool deficiency and primary secretion defect patients than in controls. In contrast, closure times with the collagen/adenosine diphosphate cartridge were normal in both delta-storage pool deficiency and primary secretion defect patients. Treatment with desmopressin increased the plasma von Willebrand Factor levels, shortened the prolonged bleeding time, shortened the closure times with the collagen/adenosine diphosphate cartridge, and normalized the closure times with the collagen/ epinephrine cartridge. Therefore, the PFA-100 test may be a less invasive alternative to the bleeding time in the diagnosis and therapeutic monitoring of patients with platelet secretion defects. The collagen/epinephrine cartridge is more sensitive than the collagen/adenosine diphosphate cartridge to defects of platelet secretion.