An interpretable prediction model for severe sepsis-associated acute kidney injury in older ICU patients with sepsis: a prospective multicenter cohort study

Severe sepsis-associated acute kidney injury (severe SA-AKI) is clinically important in older adults with sepsis, but early identification remains challenging. This study aimed to characterize clinical and immuno-inflammatory features of severe SA-AKI and develop an interpretable prediction model for older ICU patients with sepsis.

This prospective multicenter cohort study enrolled older adults with sepsis admitted to five tertiary ICUs between June 2023 and December 2025. Patients were temporally assigned to a training cohort and an internal temporal validation cohort. Severe SA-AKI was defined as KDIGO acute kidney injury stage 2 or 3 within 7 days after sepsis time zero or during ICU stay. Candidate predictors collected within 24 h after time zero were evaluated in the training cohort, and a logistic regression nomogram was developed and validated.

Among 1,236 included patients, the minimum age was 65 years, and the mean age was 74.6 ± 7.5 years; 258 patients developed severe SA-AKI. The final 7-variable model included non-renal SOFA score, chronic kidney disease, log(Lactate + 1), log(IL-6 + 1), NK-cell percentage, CD4 + T-cell percentage, and C3. The model achieved AUCs of 0.917 and 0.904 in the training and validation cohorts, respectively. Brier scores were 0.086 and 0.096. Severe SA-AKI incidence increased across low-, intermediate-, and high-risk groups: 0.5%, 13.0%, and 77.5%.

A parsimonious model integrating clinical and immuno-inflammatory variables may support early severe SA-AKI risk stratification in older ICU patients with sepsis. External validation is warranted before broader clinical implementation.