title: Variable responsiveness to clopidogrel and aspirin among patients with acute coronary syndrome as assessed by platelet function tests.
abstract: Unresponsiveness to clopidogrel or aspirin has been reported in patients with acute coronary syndrome (ACS). Platelet aggregometry (PA) and the Impact-R [Cone and Plate(let) Analyzer (CPA) technology, measuring whole blood platelet adhesion under flow conditions] were compared in detecting laboratory unresponsiveness to clopidogrel and aspirin among ACS patients. Platelet-rich plasma (PRP) samples were evaluated in 404 patients by PA using adenosine diphosphate (ADP) and arachidonic acid (AA) and whole blood samples by the Impact-R ADP- and AA-response tests. The first cohort (n=114) was assayed by PA on days 1 and 4 of the onset of ACS. A patient with relative decrease of </=10% in ADP-induced maximal platelet aggregation after clopidogrel treatment was defined as laboratory non-responding (NR) patient to clopidogrel. This relative value correlated well with an absolute value of ADP-induced aggregation >/=70%. A patient with an absolute value of AA-induced maximal aggregation >/=60% was defined as laboratory NR patient to aspirin. The second cohort (n=290) was tested on day 4 by both systems and results analyzed by receiver operating characteristic curve. The following cut-off values of the Impact-R surface coverage were obtained: </=2.8% and </=3.4% for clopidogrel and aspirin NR patients, respectively. The incidence of NR patients to clopidogrel and aspirin, according to the two methods was 27% and 22%, respectively. Impact-R compared to PA in detecting clopidogrel and aspirin NR patients revealed: 79% and 82% agreement, 71% and 73% sensitivity, 83% and 86% specificity, respectively. In conclusion, the Impact-R and PA results demonstrated high degree of similarity.
authors.affiliation: Amalia Biron Research Institute of Thrombosis and Hemostasis, Israel.
authors.forename: Boris
authors.initials: B
authors.lastname: Shenkman
authors.forename: Shlomi
authors.initials: S
authors.lastname: Matetzky
authors.forename: Paul
authors.initials: P
authors.lastname: Fefer
authors.forename: Hanoch
authors.initials: H
authors.lastname: Hod
authors.forename: Yulia
authors.initials: Y
authors.lastname: Einav
authors.forename: Aharon
authors.initials: A
authors.lastname: Lubetsky
authors.forename: David
authors.initials: D
authors.lastname: Varon
authors.forename: Naphtali
authors.initials: N
authors.lastname: Savion
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood / Q000188:drug therapy*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000328:Adult; D000368:Aged; D016718:Arachidonic Acid / Q000494:pharmacology; D001241:Aspirin / Q000008:administration & dosage*; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation / Q000379:methods; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests / Q000295:instrumentation / Q000379:methods*; D053657:Platelet-Rich Plasma / Q000187:drug effects; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D010975:Platelet Aggregation Inhibitors; D016718:Arachidonic Acid; D000244:Adenosine Diphosphate; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin