Prognostic value of the systemic immune-inflammation index in acute limb ischemia undergoing endovascular therapy

Acute limb ischemia (ALI) is a vascular emergency associated with major amputation and mortality, highlighting the need for early risk stratification. The systemic immune-inflammation index (SII), calculated from platelet, neutrophil, and lymphocyte counts, is a composite biomarker reflecting systemic inflammation and immune status. Although SII has demonstrated prognostic value in various cardiovascular diseases, its role in patients with ALI undergoing endovascular therapy remains unclear.

To evaluate the association between baseline SII and 12-month outcomes in patients with ALI undergoing endovascular therapy.

This retrospective, single-center cohort study included 47 consecutive patients with ALI treated with endovascular therapy. Patients were dichotomized at the median baseline SII into high and low SII groups. The primary outcome was a composite of major amputation or all-cause mortality within 12 months. Kaplan-Meier survival analysis and multivariable Cox proportional hazards regression models were performed to assess associations between baseline SII and outcomes, adjusting for age, sex, severe ischemia (Rutherford IIb-III), and renal function (eGFR). Receiver operating characteristic analysis evaluated the discriminatory ability of SII.

The primary outcome occurred in 20 patients (42.6%) and was more frequent in the high-SII group than in the low-SII group (62.5% vs. 21.7%, P = 0.008). Kaplan-Meier analysis demonstrated a higher event rate in the high-SII group (log-rank test, P = 0.002). In an exploratory multivariable Cox model, older age and high SII were associated with the primary composite outcome, although the estimate for high SII was imprecise with a wide confidence interval. Receiver operating characteristic analysis showed an area under the curve of 0.81 for SII, and exploratory comparisons did not demonstrate superiority of SII over the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, or C-reactive protein.

In this exploratory cohort study, elevated baseline SII was associated with a higher risk of the composite outcome of major amputation or all-cause mortality within 12 months in patients with ALI undergoing endovascular therapy. This association appeared to reflect overall adverse prognosis, whereas its specific association with major amputation remains uncertain. These findings, including the ROC-based analyses, should be considered hypothesis-generating and require validation in larger prospective multicenter studies.