Comparison at the O'Brien filter test and the PFA-100 platelet analyzer inthe laboratory diagnosis of von Willebrand's disease

Von Willebrand's disease (vWD) is the most common congenital haemorrhagic d iathesis, characterized by the quantitative or qualitative disorder of von Willebrand factor (vWF). A number of methods have been used for the diagnos is of the disease, and the bleeding time determination is widely accepted a s a screening test in spite of its low sensitivity. Our aim was to evaluate and compare the performance of two high shear systems (the O'Brien filter test and the PFA-100 device) in the screening and diagnosis of vWD. Thirty patients (n=13 type 1 with mild symptoms, n = 9 type 1 with severe symptoms , n = 2 type 2A, n =3 type 2B and n = 3 type 3 vWD) and twenty controls wer e investigated. In mild vWD the platelet retention in the second phase of t he tilter test with citrated blood showed the highest sensitivity (91.6%). The sensitivity of the PFA-100 method with collagen-epinephrine cartridges in this group was 76.9%, while the bleeding time was prolonged only in 15.4 % of the cases. In severe type 1, in type 2A and type 3 all functional test s reflected the bleeding tendency of the patients. In type 2B disease the b leeding time was prolonged only when the patient was thrombocytopenic. but both high shear systems revealed the disease independently of the presence of thrombocytopenia. The overall sensitivity of the bleeding time determina tion was 50% compared to the 80-90% sensitivity of the O'Brien Filter test and the PFA-100 system. The sensitivity values of the filter test and the P FA-100 device with collagen-epinephrine cartridges were In the same range, but the collagen-ADP cartridges showed a lower (65.5%) sensitivity, though the results were specific and had high positive predictive value. We conclu de that both high shear systems are suitable for the screening of; vWD, and that they are superior to the traditional bleeding time determination In c ase of mild disease or type 2B vWD.