Impact of Platelet Function Test on Platelet Responsiveness and Clinical Outcome After Coronary Stent Implantation: Platelet Responsiveness and Clinical Outcome

Background and Objectives: The aim of this study was to confirm the predictive cut-off values for P2Y12 reaction units (PRU) and aspirin reaction units (ARU) and to evaluate the clinical impact of $VerifyNow^{(R)}$ assays. Subjects and Methods: From November 2007 to October 2009, 186 eligible patients were prospectively recruited. Post-treatment platelet reactivity was measured by $VerifyNow^{(R)}$ assays within 12 to 24 hours after intervention, followed by standard dual maintenance dose therapy for 1 year. All patients had scheduled clinical follow-ups at 1, 3, 6, and 12 months. Results: The rate of low responders to clopidogrel, aspirin, and both drugs were 41.4%, 10.2%, and 3.8%, respectively. The predictive factors for low responsiveness to clopidogrel (PRU ${\geq}$240) were female sex, age, and non-use of cilostazol medication in our univariate analysis and age ${\geq}$65 years and non-use cilostazol in the multivariate analysis. The predictors of low responsiveness to aspirin (ARU ${\geq}$550) were male sex and age in both univariate and multivariate analyses. There was no significant difference in the clinical event rate with a cut-off value of PRU ${\geq}$240 or ARU ${\geq}$550 for 30 days and 1-year (p>0.05). Conclusion: Hyporesponsiveness to antiplatelet agents (namely aspirin and clopidogrel) was identified in about half of the patients. The cut-off point of PRU ${\geq}$240 or ARU ${\geq}$550 did not confer predictive value for 30-day or 1-year clinical event rates in patients who had undergone coronary intervention with drug-eluting stents.