Association Between Serum Ferritin and In-hospital Mortality in Critical Ills with Sepsis-Associated Acute Kidney Injury: A Retrospective Cohort Study

Background: The association between serum ferritin (SF) and in-hospital mortality in sepsis-associated acute kidney injury (SAAKI) remains unclear. The study explored the relationship between SF and in-hospital mortality in SAAKI patients. Methods: A retrospective cohort study was conducted using data from the Medical Information Mart for Intensive Care-IV2.2 database. The primary outcome was all-cause, in-hospital mortality. Multivariable adjusted Cox regression models were utilized to determine the hazard ratio (HR) and 95% confidence interval (95% CI). The natural logarithm of SF (SF(ln)) was employed for restricted cubic spline regression and threshold effects analyses. Stratified and interaction analyses in different subgroups were performed to assess the relationship's stability. Results: The study included 2,806 SAAKI patients in the intensive care unit, with a 54.1% male enrollment rate and a mean age of 64.8 ± 16.6 years. After adjusting for potential confounders, SF(ln) was found to be associated with in-hospital mortality among SAAKI patients (HR 1.27; 95% CI, 1.18-1.36; p <0.001). Patients in the highest SF quantile (Q4, SF≥1056.2ng/mL) had an adjusted HR for in-hospital mortality of 1.64 (95% CI, 1.23-2.19; p=0.001). Non-linear associations between SF(ln) and in-hospital mortality were observed, with higher SF levels corresponding to increased mortality risk. Sensitivity analyses across different subgroups yielded consistent results.Conclusion: A nonlinear association was observed between SF and in-hospital mortality among SAAKI patients. Individuals admitted with SF ≥1056.2ng/mL had substantially increased in-hospital mortality. However, additional prospective studies are required to validate these findings.