Different methodologies for evaluating the effect of clopidogrel on platelet function in high-risk coronary artery disease patients.
BACKGROUND
Two point-of-care (POC) systems have been recently proposed as rapid tools with which to evaluate residual platelet reactivity (RPR) in coronary artery disease (CAD) patients.


OBJECTIVE
We compared Platelet Function Analyzer-100 (PFA-100) closure times (CTs) by collagen/adenosine 5'-diphosphate (ADP) (C/ADP CT) cartridge and the VerifyNow P2Y12 Assay (VerifyNow) with light transmission aggregation (LTA) induced by 2 and 10 micromol L(-1) ADP in 1267 CAD patients on dual antiplatelet therapy who underwent percutaneous coronary intervention. We also performed the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay by cytofluorimetric analysis in a subgroup of 115 patients.


RESULTS
Cut-off values for identifying RPR were: > or = 54% and > or = 66% for LTA induced by 2 and 10 micromol L(-1) ADP respectively, and > or = 264 P2Y12 Reaction Units (PRU) for VerifyNow. The cut-off for PFA-100 C/ADP CT was > or = 68 s. RPR was detected in 25.1% of patients by 2 mumol L(-1) ADP-induced LTA (ADP-LTA), in 23.2% by 10 micromol L(-1) ADP-LTA, in 24.4% by PFA-100, and in 24.7% by VerifyNow. PFA-100 results did not parallel those obtained with LTA. VerifyNow showed a significant correlation (rho = 0.62, P < 0.001) and significant agreement (k = 0.34, P < 0.001) with LTA induced by 2 micromol L(-1) ADP. The correlation was similar but the agreement was better between VerifyNow and 10 micromol L(-1) ADP-LTA (rho = 0.64, P < 0.0001; k = 0.43, P < 0.001). Significant relationships were found between VASP platelet reactivity index and both ADP-LTA and VerifyNow. PFA-100 C/ADP CT did not significantly correlate with any of the other assays.


CONCLUSIONS
Our results show a significant correlation between LTA and VerifyNow but not the PFA-100 C/ADP assay. Clinical validation studies for POC systems are necessary.
Paniccia
R
R
Department of Medical and Surgical Critical Care, Thrombosis Centre, University of Florence, Florence, Itlay. rita.paniccia@unifi.it
Antonucci
E
E
Gori
A M
AM
Marcucci
R
R
Giglioli
C
C
Antoniucci
D
D
Gensini
G F
GF
Abbate
R
R
Prisco
D
D
D000368:Aged; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D000077144:Clopidogrel; D003324:Coronary Artery Disease / Q000188:drug therapy* / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D012307:Risk Factors; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000627:therapeutic use
D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine