Clopidogrel response: head-to-head comparison of different platelet assays to identify clopidogrel non responder patients after coronary stenting

Arch Cardiovasc Dis. 2010 Jan;103(1):39-45. doi: 10.1016/j.acvd.2009.11.004. Epub 2010 Jan 25.


Objectives: We investigated the agreement between different platelet tests to identify clopidogrel non response.

Background: Biological definition of clopidogrel non response remains controversial. Different platelet tests have been linked with recurrent ischemic events and proposed for daily practice.

Methods: We prospectively investigated the agreement of platelet tests to isolate clopidogrel non response in patients receiving high 150 mg clopidogrel maintenance dose after coronary stenting. Clopidogrel response was assessed with ADP-induced aggregation (ADP-Ag) (non response if >70%), Platelet reactivity index VASP (PRI VASP) (non response if >50%) and Verify Now Point-of-care assay (VN) (non response if PRU > 240 AU).

Results: Seventy consecutive patients were included. The rates of non-responders were respectively: 13% (n = 9) with the ADP-Ag, 39% (n = 27) with the PRI VASP and 33% (n = 23) with the VN. We observed significant correlation between different platelet tests assessing clopidogrel response: r = 0.55 (p < 0.0001) for ADP-Ag and PRI VASP, r = 0.64 (p < 0.0001) for ADP-Ag and VN and r = 0.59 (p < 0.0001) for PRI VASP and VN. However, using the most common thresholds, the agreement between the difference tests was poor: 0.35 for ADP-Ag and PRI VASP, 0.36 for ADP-Ag and VN and 0.46 for PRI VASP and VN.

Conclusion: This study showed that assessment of platelet function inhibition by clopidogrel is highly test-specific. Indeed, our results demonstrated a poor agreement between different platelet assays and suggested that identification of clopidogrel non responders is test-dependent.

Publication types

  • Comparative Study

MeSH terms

  • Acute Coronary Syndrome / blood
  • Acute Coronary Syndrome / therapy*
  • Adenosine Diphosphate
  • Aged
  • Angioplasty, Balloon, Coronary / instrumentation*
  • Blood Platelets / drug effects*
  • Blood Platelets / metabolism
  • Cell Adhesion Molecules / blood
  • Clopidogrel
  • Drug Resistance*
  • Female
  • Humans
  • Linear Models
  • Male
  • Microfilament Proteins / blood
  • Middle Aged
  • Phosphoproteins / blood
  • Platelet Aggregation / drug effects
  • Platelet Aggregation Inhibitors / therapeutic use*
  • Platelet Function Tests* / methods
  • Point-of-Care Systems
  • Predictive Value of Tests
  • Prospective Studies
  • Purinergic P2 Receptor Antagonists
  • Receptors, Purinergic P2 / blood
  • Receptors, Purinergic P2Y12
  • Stents*
  • Ticlopidine / analogs & derivatives*
  • Ticlopidine / therapeutic use


  • Cell Adhesion Molecules
  • Microfilament Proteins
  • P2RY12 protein, human
  • Phosphoproteins
  • Platelet Aggregation Inhibitors
  • Purinergic P2 Receptor Antagonists
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2Y12
  • vasodilator-stimulated phosphoprotein
  • Adenosine Diphosphate
  • Clopidogrel
  • Ticlopidine