Association of Aggregate Index of Systemic Inflammation (AISI) with all-cause mortality in critically Ill pediatric patients: a retrospective cohort study

Growing evidence supports the prognostic utility of AISI in adults, but its association with mortality in the critically ill pediatric population remains poorly characterized. To investigate the association between AISI and 28-day all-cause mortality in critically ill pediatric patients. A total of 8,797 patients admitted to the pediatric intensive care unit were included from the PIC Database. The AISI was log₂-transformed and categorized into four groups based on quartiles. The outcomes included 28-day all-cause mortality, both in-hospital and in-ICU. Cox proportional hazards regression, restricted cubic spline, two-piecewise threshold model, and subgroup analyses were used to evaluate the association between AISI and 28-day all-cause mortality. Males accounted for 4,930 (56.0%) of the patients. The overall 28-day in-hospital and ICU all-cause mortality rates were 4.3% and 4.2%, respectively. The RCS analysis revealed a significant nonlinear association between the log 2 -transformed AISI and both mortality outcomes. Threshold effect analysis identified that the threshold points of log₂-AISI were 5.410 and 5.407 for 28-day in-hospital and ICU mortality, respectively. Subgroup analyses revealed no notable differences between specific patient subgroups. This study suggests a nonlinear association between AISI and 28-day mortality in critically ill pediatric patients. AISI levels above the threshold were independently associated with an increased mortality risk.