Abstract

Heart failure (HF) is one of the most common clinical syndromes and a leading cause of morbidity and mortality worldwide, affecting 64 million people. The Systemic Immune-Inflammation Index (SII) is a new composite biomarker from standard blood tests that also reflects the imbalance between inflammation and immune response, thrombosis, and adaptive immunity and may capture the multifactorial immune imbalance in cardiovascular diseases. This systematic review and diagnostic accuracy meta-analysis assessed the prognostic value of SII in adult patients with HF while clarifying its role in clinical decision-making. A comprehensive systematic search of the literature was conducted in the electronic databases PubMed, Web of Science, Scopus, and Embase from their inception until August 2025. Six studies were included in the systematic analysis. The current analysis showed a significant association (HR = 1.64, 95% CI: 1.21, 2.22, p < 0.0001), with high heterogeneity. The sensitivity was 73% (95% CI: 0.62-0.82), and the specificity was 70% (95% CI: 0.57-0.81). The diagnostic odds ratio was 6.34 (95% CI: 2.95-13.6). The likelihood ratio for a positive test was 2.45 (95% CI: 1.59-3.76) and for a negative test 0.387 (95% CI: 0.259-0.578). The false positive rate was 0.297 (95% CI: 0.191-0.43). To summarize, the current evidence indicated only moderate accuracy, limiting its utility as a sole predictor of mortality. Its greatest value might be in combination with existing risk models, and further large, prospective studies are needed to validate its clinical utility and refine its application.

Key words: Systemic immune-inflammation index, heart failure, prognosis, mortality, inflammation, meta-analysis