Correlation Analysis of the New Inflammatory Composite Index with the Degree of Coronary Artery Lesions in Elderly Patients

Background: Systemic inflammation plays a key role in the development and progression of coronary artery disease (CAD). However, the clinical relevance of hematologic inflammatory indices in elderly patients has not been fully clarified. Objective: To investigate the association of five hematologic inflammatory indices—neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI)—with the presence and severity of CAD in an elderly population. Methods: This retrospective single-center study included 582 consecutive patients aged ≥ 60 years who underwent coronary angiography between 2021 and 2023. Based on the extent of coronary artery involvement, patients were categorized into four groups: normal (n = 131), single-vessel disease (n = 133), two-vessel disease (n = 136), and three-vessel disease (n = 182). Inflammatory indices were calculated from routine blood counts. Group differences were assessed using the Kruskal–Wallis test. Multivariable logistic regression analysis was performed after adjustment for age, sex, body mass index, hypertension, and diabetes. Discriminatory performance was evaluated using receiver operating characteristic (ROC) curve analysis with comparisons conducted by the DeLong test. Results: All five inflammatory indices were significantly associated with increasing angiographic severity of CAD (all P < 0.05). Among them, SIRI demonstrated the strongest independent association (OR = 4.91, 95% CI: 2.11– 11.44) and the highest area under the ROC curve (AUC = 0.766), followed by SII (AUC = 0.749). The addition of inflammatory indices to conventional risk factors modestly improved model discrimination. Conclusion: This study demonstrates that SIRI and SII are valuable inflammatory biomarkers for evaluating the severity of coronary artery disease in elderly patients, highlighting the role of systemic inflammation in the progression of age-related atherosclerosis. As the first systematic comparison of five hematologic composite indices in a geriatric cohort, our findings suggest that SII and SIRI—both cost-effective and readily available parameters—are closely associated with CAD severity, though prospective studies are needed to establish their clinical value. Keywords: elderly patients, coronary artery disease, systemic inflammation response index, systemic immune-inflammation index, hematologic inflammatory indices