The association between systemic immune-inflammation index and the short-term functional outcome of patients with aneurysmal subarachnoid hemorrhage: a meta-analysis.

Abstract

Systemic immune-inflammation index (SII), calculated as platelet count × neutrophil count/lymphocyte count, is a novel biomarker reflecting immune and inflammatory responses. Its prognostic value in patients with subarachnoid hemorrhage (SAH) remains unclear. This meta-analysis aimed to evaluate the association between SII at admission and the short-term functional outcomes of patients with SAH. A systematic search of PubMed, Embase, Web of Science, China National Knowledge Infrastructure, and Wanfang databases identified cohort studies reporting the relationship between SII levels and functional outcomes in SAH. Poor functional outcomes were defined as modified Rankin Scale > 2 or Glasgow Outcome Scale < 4. Heterogeneity was assessed using I² statistic, and data synthesis was performed using a random-effects model by incorporating the influence of heterogeneity. RevMan 5.1 and Stata 17.0 were used for the analyses. Ten cohort studies involving 2,228 patients were included. Meta-analysis revealed that a high SII at admission significantly increased the risk of poor functional outcomes (OR: 3.08, 95% CI: 2.07-4.59, p < 0.001) with moderate heterogeneity (I² = 61%). Subgroup analysis showed a stronger association in studies with SII cutoffs ≥ 1400 compared to < 1400 (p for subgroup difference < 0.001). Meta-regression identified the cutoff value for SII as a significant modifier (p = 0.03) for the association between SII and poor functional outcome. Sensitivity analyses by excluding one dataset at a time showed similar results (p all < 0.05). In conclusion, elevated SII at admission is associated with an increased risk of poor short-term functional outcomes in SAH. These findings highlight SII as a potential prognostic biomarker for early risk stratification in SAH patients.