Anciximab provides potent, but variable degrees of platelet inhibition both
during the duration of intravenous administration and at 12 hours followin
g therapy. Platelet function was assessed using the PC-RPFA system in 78 pa
tients scheduled for percutaneous coronary revascularization who were admin
istered the standard abciximab weight-adjusted bolus and 12-hour infusion.
The PC-RPFA system is a cartridge-based, semiautomated point-of-care whole-
blood assay that incorporates fibrinogen-coated polystyrene beads, buffers,
and a modified thrombin receptor activating peptide (Isotrap) in lyophiliz
ed form. The instrument detects the agglutination rate between the stimulat
ed platelets and the fibrinogen-coated beads, and provides a quantitative d
igital display in less than 2 minutes. No differences in the level of plate
let inhibition were observed in these abciximab-treated patients by diabeti
c status, gender, smoking, diagnosis (unstable angina, chronic stable angin
a, recent myocardial infarction), or abciximab treatment status (first time
vs. retreatment). Nocorrelation of the PC-RPFA rate of platelet aggregatio
n with clinical demographic factors was observed, with the exception of bas
eline hematocrit (r(2) = 0.4556). The relationship between the PC-RPFA rate
of aggregation and hematocrit reflects light absorbance by erythrocytes an
d is specific to the PC-RPFA system. The absolute rate of platelet aggregat
ion (slope) reported by the PC-RPFA is correlated with percent aggregation,
thus making it potentially possible to predict the level of aggregation wi
thout reference to a baseline (pretreatment) measure of platelet function.
This correlation was closest for patients having < 40% baseline aggregation
(r(2) = 0.55). Thus, PC-RPFA provides a rapid point-of-care assessment of
platelet function that could allow for adjustment of abciximab dosing to ac
hieve targeted levels of platelet inhibition. The utility of this device to
optimize therapy with platelet glycoprotein IIb/IIIa inhibitors is current
ly being evaluated.