DESCRIPTION OF AN IN-VITRO PLATELET-FUNCTION ANALYZER - PFA-100(TM)

A new in vitro system for the detection of platelet dysfunction, PFA-1 00(TM), has been developed. It provides a quantitative measure of pla telet function in anticoagulated whole blood. The system comprises a m icroprocessor-controlled instrument and a disposable test cartridge co ntaining a biologically active membrane. The instrument aspirates a bl ood sample under constant vacuum from the sample reservoir through a c apillary and a microscopic aperture cut into the membrane. The membran e is coated with collagen and epinephrine or adenosine 5'-diphosphate. The presence of these biochemical stimuli, and the high shear rates g enerated under the standardized flow conditions, result in platelet at tachment, activation, and aggregation, slowly building a stable platel et plug at the aperture. The time required to obtain full occlusion of the aperture is reported as the ''closure time.'' We have found that impairment of von Willebrand factor, or inhibition of platelet recepto rs glycoprotein Ib or IIb/IIIa with monoclonal antibodies or peptides, resulted in abnormal closure times. An antifibrinogen antibody, in co ntrast, failed to show any effect. The test appears to be sensitive to platelet adherence and aggregation abnormalities. The PFA-100(TM) sys tem has potential applications in routine evaluation of platelet funct ion in the clinical setting because of its accuracy, ease of operation , and rapid turnaround of results.