[Dual association of peripheral blood eosinophil count with high on-treatment platelet reactivity and long-term cardiac death in patients with coronary artery disease: a large-scale cohort study].

Objective: To investigate the association of baseline peripheral blood eosinophil count with high on-treatment platelet reactivity and its clinical prognostic value in patients with coronary artery disease undergoing percutaneous coronary intervention (PCI) and receiving clopidogrel. Methods: This was a single-center prospective cohort study. Consecutive patients with coronary artery disease who underwent PCI at Fuwai Hospital, Chinese Academy of Medical Sciences, between January and December 2013 were enrolled; those receiving dual antiplatelet therapy with aspirin and clopidogrel were included. Baseline data were collected, and platelet reactivity was assessed using thromboelastography. Patients were followed up for 5 years, with cardiac death as the endpoint. Baseline eosinophil count was analyzed as a continuous variable and was also categorized into quartiles (Q1-Q4). Multivariable logistic regression was used to analyze the association between eosinophil count and high on-treatment platelet reactivity. Multivariable restricted cubic spline models were used to analyze the dose-response relationship. Subgroup analyses and interaction tests were performed according to age, sex, diabetes, hypertension, acute coronary syndrome, body mass index, and high-sensitivity C-reactive protein levels. Multivariable Cox proportional hazards regression was used to assess the predictive value of eosinophil count for cardiac death. Results: A total of 6 524 patients were included. The mean age was (58.21±10.26) years, and 5 059 (77.54%) were male. Among them, 6 050 patients completed the 5-year follow-up, and 140 cardiac deaths (2.31%) occurred. Multivariable logistic regression analysis showed that peripheral blood eosinophil count was negatively associated with the risk of high on-treatment platelet reactivity (OR=0.94, 95%CI: 0.90-0.98, P=0.003). When analyzed as a categorical variable, compared with the lowest quartile group (Q1), the risk of high on-treatment platelet reactivity was lower in patients in the highest quartile group (Q4) (OR=0.77, 95%CI: 0.65-0.91, P=0.003). Multivariable restricted cubic spline analysis showed a linear negative correlation between eosinophil count and the risk of high on-treatment platelet reactivity (P for overall=0.012, P for nonlinearity=0.362). Further subgroup analysis showed that the above association remained consistent across clinical subgroups stratified by age, sex, diabetes, hypertension, acute coronary syndrome, body mass index, and high-sensitivity C-reactive protein levels (all P for interaction>0.05). Multivariable Cox regression analysis showed that peripheral blood eosinophil count was positively associated with the risk of cardiac death (HR=1.14, 95%CI: 1.07-1.21, P<0.001). When analyzed as a categorical variable, compared with the Q1 group, the risk of cardiac death was higher in patients in the Q4 group (HR=2.12, 95%CI: 1.25-3.59, P<0.001). Conclusions: In patients with coronary artery disease undergoing PCI and receiving clopidogrel, baseline peripheral blood eosinophil count showed a dual association with high on-treatment platelet reactivity and long-term cardiac death. A lower count was associated with an increased risk of high on-treatment platelet reactivity, whereas an elevated count was associated with an increased long-term risk of cardiac death.