Systemic immune‐inflammation index (SII) predicted clinical outcome in patients with coronary artery disease

Abstract Background This study examines the predictive value of a novel systemic immune‐inflammation index (SII, platelet × neutrophil/lymphocyte ratio) in coronary artery disease (CAD) patients. Methods A total of 5602 CAD patients who had undergone a percutaneous coronary intervention (PCI) were enrolled. They were divided into two groups by baseline SII score (high SII vs low SII) to analyse the relationship between SII groups and the long‐term outcome. The primary outcomes were major cardiovascular events (MACE) which includes nonfatal myocardial infarction (MI), nonfatal stroke and cardiac death. Secondary outcomes included a composite of MACE and hospitalization for congestive heart failure. Results An optimal SII cut‐off point of 694.3 × 10 9 was identified for MACE in the CAD training cohort (n = 373) and then verified in the second larger CAD cohort (n = 5602). Univariate and multivariate analyses showed that a higher SII score (≥694.3) was independently associated with increased risk of developing cardiac death (HR: 2.02; 95% CI: 1.43‐2.86), nonfatal MI (HR: 1.42; 95% CI: 1.09‐1.85), nonfatal stroke (HR: 1.96; 95% CI: 1.28‐2.99), MACE (HR: 1.65; 95% CI: 1.36‐2.01) and total major events (HR: 1.53; 95% CI: 1.32‐1.77). In addition, the SII significantly improved risk stratification of MI, cardiac death, heart failure, MACE and total major events than conventional risk factors in CAD patients by the significant increase in the C‐index ( P < .001) and reclassification risk categories by significant NRI ( P < .05) and IDI ( P < .05). Conclusions SII had a better prediction of major cardiovascular events than traditional risk factors in CAD patients after coronary intervention.