title: Comparison of four tests to assess inhibition of platelet function by clopidogrel in stable coronary artery disease patients.
abstract: OBJECTIVE
  We investigated the comparability of platelet function tests in quantifying platelet inhibition achieved by clopidogrel.
  
  
  RESULTS
  This pre-specified substudy of a randomized, double-blind trial included 116 patients with stable coronary artery disease requiring diagnostic angiography. Patients received clopidogrel for 1 (300 or 600 mg) or 7 days (300 + 75 or 150 mg daily) before the procedure. Blood samples obtained before clopidogrel initiation and before diagnostic coronary angiography were assayed using light transmission aggregometry [adenosine diphosphate (ADP) 5 and 20 microM as the agonist], whole-blood aggregometry (ADP 5 and 20 microM), PFA-100 (Collagen-ADP cartridge), and VerifyNow P2Y12. Although all assays studied were found sensitive to clopidogrel ingestion, none could distinguish categorically between patients who had, or not, ingested clopidogrel. Agreement between assays to identify patients with insufficient inhibition of platelet aggregation by clopidogrel was low.
  
  
  CONCLUSIONS
  The assessment of platelet function inhibition by clopidogrel is highly test-specific. Decision to increase clopidogrel dosage may vary on the basis of the assay used, thus highlighting the need for unambiguous guidelines with respect to assay selection, as platelet function assays are not interchangeable. At present, platelet function testing evaluating clopidogrel efficacy cannot be recommended in routine clinical practice.
authors.affiliation: Faculty of Pharmacy, Université de Montréal, Montréal, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Lordkipanidzé
authors.forename: Chantal
authors.initials: C
authors.lastname: Pharand
authors.forename: Thuy Anh
authors.initials: TA
authors.lastname: Nguyen
authors.forename: Erick
authors.initials: E
authors.lastname: Schampaert
authors.forename: Donald A
authors.initials: DA
authors.lastname: Palisaitis
authors.forename: Jean G
authors.initials: JG
authors.lastname: Diodati
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000008:administration & dosage*; D000077144:Clopidogrel; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000097:blood* / Q000000981:diagnostic imaging; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests / Q000592:standards; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin