The aggregate index of systemic inflammation is positively correlated with the risk of all-cause mortality in sepsis-associated acute kidney injury

Sepsis is a major health problem worldwide, and sepsis-associated acute kidney injury (SA-AKI) patients usually experience severe conditions, high mortality, and long length of stay. The predictive value of aggregate index of systemic inflammation (AISI) in the prognosis of several diseases has been documented. This study intends to investigate the association between AISI and mortality in SA-AKI. Data of patients with SA-AKI first admitted to the intensive care unit in 2008-2019 were acquired from the Medical Information Mart for Intensive Care IV (MIMIC-IV). The impact of AISI on 30-/90-/180-d and 1-year mortality in SA-AKI was investigated by Cox proportional hazard regression models, Kaplan-Meier analyses, and restricted cubic spline (RCS) analyses. Moreover, subgroup analyses, stratified by gender, comorbidity, and intervention, were conducted. Totally 9714 SA-AKI patients were included, and they were assigned into a Low AISI Group (AISI < 735.405 × 10¹⁸/L) and a High AISI Group (AISI ≥ 735.405 × 10¹⁸/L) based on the median of AISI. As revealed by the regression model, 30-/90-/180-d and 1-year mortality in SA-AKI was higher in the High AISI Group than in the Low AISI Group (P < 0.05). Kaplan-Meier analyses confirmed higher 30-/90-/180-d and 1-year survival rates in the Low AISI Group (P_log-rank<0.0001). Using RCS curves, we also found a nonlinear relation between AISI and 30-/90-/180-d, and 1-year mortality in SA-AKI (P_nonlinear<0.001). Subgroup analyses suggested no interaction of AISI with the stratified variables (P_interaction>0.05), and the association of AISI with 30-d mortality was consistent across subgroups. In Conclusion, AISI has an association with mortality in SA-AKI. Quantitative stratification of AISI at admission may contribute to early detection and treatment of SA-AKI with a poor prognosis.