Testing platelet activation with a shear-dependent platelet function test versus aggregation-based tests: relevance for monitoring long-term glycoprotein IIb/IIIa inhibition.
BACKGROUND
Tests developed to monitor glycoprotein (GP) IIb/IIIa blockade do not properly reflect platelet function in vivo and need a baseline (pretreatment) value. Because GP IIb/IIIa is essential in platelet aggregation and thrombosis under shear conditions, a flow-dependent approach to monitor its inhibition can be used.


RESULTS
We compared a test based on flow-dependent platelet deposition, the Cone and Platelet Analyzer (CPA), with in vitro platelet aggregometry and the Rapid Platelet Function Assay (RPFA) on platelet function after GP IIb/IIIa inhibition. In vitro, increasing concentrations of abciximab (0% to 100% receptor occupancy) were tested. Ex vivo, platelet function was monitored with the CPA and with aggregometry for up to 1 week after abciximab administration. The CPA was better correlated with the percentage of free GP IIb/IIIa receptors than was aggregometry or the RPFA. Only the RPFA, when expressed as a ratio over baseline (pretreatment), was comparable to the CPA. Ex vivo, the CPA, but not aggregometry, showed prolonged platelet inhibition with gradual recovery from GP IIb/IIIa receptor blockade in the first week after abciximab administration.


CONCLUSIONS
Platelet function assessment by shear-induced deposition is a reliable test to monitor a wide range of GP IIb/IIIa inhibition. Its accuracy does not require a baseline reference. The effects of GP IIb/IIIa blockade on platelet function should be examined under high shear conditions.
Osende
J I
JI
Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY, USA.
Fuster
V
V
Lev
E I
EI
Shimbo
D
D
Rauch
U
U
Marmur
J D
JD
Richard
M
M
Varon
D
D
Badimon
J J
JJ
D000077284:Abciximab; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018955:CD36 Antigens / Q000378:metabolism*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D066298:In Vitro Techniques; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010979:Platelet Function Tests / Q000379:methods; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D018955:CD36 Antigens; D007140:Immunoglobulin Fab Fragments; D010975:Platelet Aggregation Inhibitors; D019038:Platelet Glycoprotein GPIb-IX Complex; D000077284:Abciximab