Prognostic value of systemic immune‐inflammation index in CAD patients: Systematic review and meta‐analyses

Abstract Background Systemic immune‐inflammation index (SII) is a novel inflammatory marker based on neutrophils, platelets and lymphocytes counts, which has potential prognostic value among coronary artery disease (CAD) patients as described by some observational studies. We aimed to provide higher‐certainty evidence to verify the association of SII with poor outcomes of CAD patients. Methods PubMed, Web of Science, Embase, Ovid and Scopus were searched to find relevant literature exploring the prognostic value of SII among CAD patients. Hazard ratios (HRs) with 95% confidence intervals (CIs) extracted from the literature included were pooled with the fixed‐effect or random‐effect model. Sensitivity analyses and subgroup analyses were conducted to detect the source of heterogeneity and evaluate the stability of results. Results A total of nine studies with 15,832 participants were included. The quantitative synthesis including eight studies with 15,657 participants showed that the high SII was related to the major adverse cardiovascular event in CAD patients (HR with 95% CI: 2.36 [1.67, 3.33]). After eliminating heterogeneity and adjusting for publication bias, the above result was still robust (HR with 95% CI: 1.67 [1.32, 2.12]). Additionally, we also demonstrated the prognostic values of SII for all‐cause death, cardiovascular death, myocardial infarction and stroke. Conclusion Higher SII has prognostic values for adverse outcomes in CAD patients.