Dual antiplatelet therapy (DAPT) with standard doses of aspirin and clopidogrel has long been the cornerstone in patients undergoing percutaneous coronary intervention (PCI). However, inhibition of platelet activation and aggregation after DAPT varies greatly among patients. Some clinical studies have demonstrated that patients with high on-treatment platelet reactivity are at increased risk of major adverse cardiovascular events. Tailored antiplatelet therapy seems offer an opportunity to improve outcomes after coronary stenting by drug adjustment based on platelet function testing. Unfortunately, the results of 3 major prospective trials (GRAVITAS, ARCTIC, TRIGGER PCI) of personalized antiplatelet therapy are neutral. In these studies, platelet function was only assessed by a single measurement and a single method early after the start of antiplatelet treatment. To test the stability of platelet reactivity measurements over time among patients undergoing PCI, investigators use 3 methods (VerifyNow P2Y12 assay, Flow cytometric assessment of the phosphorylation status of VASP, light transmittance aggregometry) for platelet function testing in 2 periods (~14days), with maintenance doses of clopidogrel.

Inclusion Criteria:

1. >18 years old.

2.15 ≤ eGFR < 60 ml/min/1.73 m2.

3. Clinically stable and following PCI between 4 weeks and 1 year.

4. On clopidogrel (75mg/d) and aspirin (100mg/d) treatment at least 4 weeks.

Exclusion Criteria:

1. Conditions that alter platelet function.
2. Conditions that increase bleeding risk.

Dual antiplatelet therapy (DAPT) with standard doses of aspirin and clopidogrel has long been the cornerstone in patients undergoing percutaneous coronary intervention (PCI). However, inhibition of platelet activation and aggregation after In these studies, platelet function was only assessed by a single measurement and a single method early after the start of antiplatelet treatment. To test the stability of platelet reactivity measurements over time among patients undergoing PCI, we use 3 methods (VerifyNow P2Y12 assay, Flow cytometric assessment of the phosphorylation status of VASP, light transmittance aggregometry) for platelet function testing in 2 periods (~14days), with maintenance doses of clopidogrel.