Renal Angina Index for Predicting Acute Kidney Injury in Adult ICU Patients

Acute kidney injury (AKI) is a frequent complication of critical illness and is associated with increased morbidity and mortality. Early identification of patients at risk of progressing to moderate-to-severe AKI may facilitate closer monitoring and timely implementation of kidney-protective strategies. This prospective observational cohort study will evaluate the predictive performance of the Renal Angina Index (RAI) for the development of Kidney Disease: Improving Global Outcomes (KDIGO) stage 2 or stage 3 AKI in adult intensive care unit patients. Consecutive eligible patients admitted to the participating adult intensive care unit will be enrolled. The RAI will be calculated 24 hours after ICU admission using routinely available clinical characteristics and the change in serum creatinine between ICU admission and 24 hours. The primary outcome will be the development of KDIGO stage 2 or stage 3 AKI during the subsequent 48 hours. AKI staging will incorporate serum creatinine, urine-output, and renal replacement therapy criteria according to KDIGO definitions. The predictive performance of RAI will be evaluated using receiver operating characteristic analysis and the prespecified RAI threshold of ≥10. Secondary outcomes will include 7-day and 30-day intensive care unit mortality, intensive care unit length of stay, and duration of invasive mechanical ventilation.