Systemic immune-inflammation index as a risk factor for acute kidney injury in patients with neonatal jaundice.

BACKGROUND: Acute kidney injury (AKI) is a serious complication in patients with neonatal jaundice, and inflammation is key to its development. The systemic immune-inflammation index (SII) has been associated with AKI in adults, but its role in jaundiced neonates is unknown. This study aimed to assess the association between SII and AKI risk in this population. METHODS: This retrospective study utilized data from the Medical Information Mart for Intensive Care-IV database, including 2,326 patients with neonatal jaundice. Due to skewed SII distribution, log2-transformed SII (logSII) was used. Logistic regression was used to analyze the logSII-AKI association. Restricted cubic spline (RCS) analysis was used to explore the nonlinear relationship. Subgroup and interaction analyses were conducted to assess the sensitivity of the relationship across clinical characteristics. Complete-case analysis and the E-value were used to assess the robustness of the association. The correlation between logSII and neonatal intensive care unit (NICU) duration was examined using Spearman correlation analysis. RESULTS: Higher logSII was independently associated with increased AKI risk {adjusted odds ratio (OR) [95% confidence interval (CI)]: 1.230 (1.107, 1.369); P<0.001}. RCS analysis showed no significant departure from linearity (P for overall <0.001, P for non-linear =0.51), which remained robust after adjustment. The association was generally consistent across predefined subgroups (all P for interaction >0.05). The findings were robust in sensitivity analyses [E-value =1.76 for the point estimate; multiple imputation for bilirubin: OR 1.227 (1.105, 1.364); complete-case analysis: OR 1.256 (1.103, 1.431)]. Interestingly, higher logSII correlated with shorter NICU duration (Spearman r=-0.174, P<0.001). CONCLUSIONS: logSII demonstrates an independent, approximately linear association with AKI risk in jaundiced neonates. The paradoxical association with NICU duration warrants further investigation.