Association Between Albumin–Bilirubin Index and Clinical Outcomes in Septic Acute Kidney Injury Patients

Background The albumin–bilirubin index (ALBI) has been reported as a prognostic marker in various clinical conditions; however, its value in patients with septic acute kidney injury (AKI) has not been clearly evaluated. This study aimed to investigate the association between ALBI and clinical outcomes in this population. Methods This retrospective cohort study used data from the Medical Information Mart for Intensive Care IV database. ALBI was analyzed as both a continuous variable in the primary analysis and a categorical variable according to tertiles in sensitivity analysis. The primary outcomes were 28-day, 60-day, 90-day, and 1-year all-cause mortality. Secondary outcomes included intensive care unit (ICU) transfer, septic shock, and disease severity. Cox proportional hazards models were used to evaluate the association between ALBI and mortality, and restricted cubic spline analyses were performed to assess potential nonlinearity. Subgroup analyses were further conducted to examine the consistency across different sub-group populations. Results Overall, 6700 patients with septic AKI were included. In adjusted Cox models, each 1-standard deviation increase in ALBI was associated with higher risks of 28-day mortality (HR 1.16, 95% confidence interval [CI] 1.10-1.22), 60-day mortality (HR 1.14, 95% CI 1.10-1.19), 90-day mortality (HR 1.13, 95% CI 1.08-1.18), and 1-year mortality (HR 1.10, 95% CI 1.06-1.14). The association between ALBI and mortality was generally consistent across most prespecified subgroups. Higher ALBI was also linked with septic shock (odds ratio [OR] 1.15, 95%CI 1.08-1.21, P < .001), ICU transfer (OR 1.09, 95%CI 1.02-1.16), and greater disease severity. RCS curves showed a nonlinear increase in mortality risk with ascending ALBI. Sensitivity analyses based on ALBI tertiles yielded broadly consistent findings. Conclusion Higher ALBI was independently associated with increased short- and long-term mortality and adverse clinical outcomes in septic AKI patients.