Implications of the Presence of Non-obstructive Atherosclerotic Plaques on Platelet and Vascular Reactivity

The VerifyNow P2Y12® assay provides established cut-off values that allow discrimination of patients with low responsiveness to antiplatelet therapy, with higher PRU values being associated with adverse clinical outcomes. Based on this concept, it is possible to assess the impact of potential platelet hyperreactivity by analyzing the proportion of patients exceeding a predefined clinically relevant threshold. Data collected in this manner allow non-parametric statistical analysis using the McNemar test. A PRU cut-off value of 208 has been widely used in patients treated with clopidogrel and was therefore selected in the present study as the threshold defining inadequate response to the drug. Assuming a 15% difference between the case and control groups, with a statistical power of 95% and a two-sided alpha level of 0.05, a minimum sample size of 82 patients was calculated. Considering an estimated 10% rate of non-inclusion (e.g., refusal to sign informed consent or exclusion due to high Framingham risk score), the final planned sample size for the study was set at 90 participants.