The systemic immune-inflammation index is an independent predictive factor in predicting major amputation in chronic limb-threatening ischemia

BackgroundLower extremity peripheral arterial disease (LEAD) is characterized by the narrowing and occlusion of arteries in the lower extremities. The most severe form of LEAD is chronic limb-threatening ischemia (CLTI), which carries a poorer prognosis for major amputation. The systemic immune-inflammation index (SII) is an index developed to simultaneously reflect the inflammatory and immunothrombosis status of patients, based on platelet counts and the neutrophil-to-lymphocyte ratio.ObjectiveOur study aimed to investigate the relationship between elevated SII and major limb amputation.MethodThe study included 140 patients with foot wounds (Rutherford 5 or 6) due to LEAD who were scheduled for endovascular intervention between 2018 and 2023. Major amputation was required in 27 patients (19.2%). The neutrophil-to-lymphocyte ratio (2.1/2.8/3.8 vs 3.8/6.6/9.3, <i>p</i> < .001), platelet-to-lymphocyte ratio (103.8/128.8/162.9 vs 132.8/212.3/314.6, <i>p</i> < .001), and SII (527/720/1055.5 vs 1108/1951/3807, <i>p</i> < .001) were higher in the major amputation group. ROC curve analysis determined that the optimal cut-off value for SII to predict major amputation in LEAD patients was 1018, with a sensitivity and specificity of 81% and 73%, respectively (AUC: 0.84, 95% CI: 0.74-0.92, <i>p</i> < .001). Logistic regression analysis showed that high SII (OR = 1.001, 95% CI = 1-1.001, <i>p</i> = .009) was identified as an independent predictor of major amputation in LEAD patients.ConclusionThis study establishes that a high SII value is associated with major amputation in LEAD patients with foot wounds.ResultSII is a valuable and straightforward parameter for predicting major amputation risk and guiding treatment decisions in LEAD patients.