The effect of antiplatelet drugs, heparin, and preanalytical variables on platelet function detected by the platelet function analyzer (PFA-100 (R))

The platelet function analyzer (PFA)-100(R) is a newly developed instrument that provides a rapid, in vitro, quantitative measurement of platelet adhe sion and aggregation in whole blood flowing through a small aperture under high shear conditions. Thirty patients undergoing percutaneous transluminal coronary angioplasty (PTCA) and ten normal individuals were included in th is study. In vitro and in vivo studies were conducted to discern the effect of combinations of antiplatelet drugs (aspirin, ticlopidine, abciximab) an d heparin on the performance of the device as well as the effects of preana lytical variables, such as method of sample collection and ex vivo anticoag ulants. Studies were also conducted examining the effect of aperture size ( standard 150 mu m vs. smaller 120 mu m) on the ability of the device to det ect the effect of antiplatelet drugs. There was no difference in mean PFA-1 00(R) closure time with citrate versus PPACK anticoagulants or with venipun cture vs. sheath sampling. Closure times did not vary with heparin administ ration. Closure times were slightly longer for patients taking aspirin plus ticlopidine compared to aspirin alone (p = NS). In contrast adenosine disp hosphate (ADP) induced platelet aggregation was significantly less in patie nts that took aspirin plus ticlopidine vs. aspirin alone (p = .0005). In vi tro, there was a dose-dependent increase in closure time for both aperture sizes with increasing abciximab concentration. Although both cartridges sho wed infinite closure times at an abciximab concentration of 2.25 mu g/mL, t here was a slight benefit to using the 120 mu m aperture cartridges at abci ximab concentrations of 1.75 to 2.0 mu g/mL. In ten patients who were follo wed during abciximab therapy to assess the effect of aperture size, the PFA -100(R) was able to detect in vivo platelet inhibition by abciximab, but de tection of recovery from abciximab-induced platelet dysfunction was slightl y better for the PFA-100(R) with the 120 mu m aperture compared to the stan dard 150 mu m aperture collagen/ADP cartridge.