Abstract
BACKGROUND: The systemic inflammation response index (SIRI), a novel biomarker integrating neutrophil, monocyte, and lymphocyte counts, has been implicated in cardiovascular disease prognosis. This study aimed to systematically evaluate the association between SIRI and clinical outcomes in patients with myocardial infarction (MI). METHODS: A comprehensive literature search was conducted across multiple databases up to July 2025. Observational studies reporting odds ratios (ORs) with 95% confidence intervals (CIs) for the association between SIRI and post-MI outcomes were included. Pooled ORs were calculated using random-effects models. Heterogeneity and publication bias were assessed. RESULTS: Twelve comparative groups (6,751 participants) showed that elevated SIRI was possibly associated with an increased risk of major adverse cardiovascular events (MACE) (OR = 1.42, 95% CI: 1.27-1.58). SIRI was also potentially associated with higher all-cause mortality (OR = 1.28), stroke (OR = 1.11), subsequent AMI (OR = 1.21), and the Gensini score (OR = 6.89). Significant heterogeneity was observed for some outcomes. Subgroup analyses indicated that study sample size and SIRI cut-off values were potential sources of heterogeneity. CONCLUSION: An elevated SIRI is consistently associated with an increased risk of adverse clinical outcomes in patients with MI, underscoring its potential value as a readily accessible prognostic biomarker for risk stratification. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420251169048.