Role of Systemic Immune Inflammation Index in Coronary Artery Disease

Abstract

Background: Coronary artery disease (CAD) remains one of the leading causes of morbidity and mortality worldwide, primarily driven by atherosclerosis, which is now recognized as a chronic inflammatory process. Inflammation and immune activation contribute to every stage of atherogenesis, from endothelial dysfunction to plaque rupture. Traditional biomarkers such as C-reactive protein (CRP) and neutrophil-to-lymphocyte ratio (NLR) have been widely used to reflect systemic inflammation; however, their predictive value remains limited when considered alone. Recently, the Systemic Immune-Inflammation Index (SII)—calculated as platelet count × neutrophil count / lymphocyte count—has emerged as a novel and reliable biomarker that integrates three key components of the immune and inflammatory response, providing a more comprehensive assessment of vascular inflammation.

Conclusion: Accumulating evidence indicates that a high SII is significantly associated with greater severity and complexity of coronary lesions, as reflected by higher SYNTAX scores, and may predict adverse cardiovascular outcomes in patients with CAD. Owing to its simplicity, cost-effectiveness, and availability in routine blood tests, SII could serve as a valuable adjunctive tool for early risk stratification and prognostic evaluation in coronary artery disease.