External validation of the renal angina index for early prediction of severe acute kidney injury in critically ill children: a prospective cohort study from Vietnam.

BACKGROUND

Acute kidney injury (AKI) is common in critically ill children and is associated with poor outcomes. The Renal Angina Index (RAI) has been proposed as an early risk stratification tool, but evidence from low- and middle-income countries remains limited.

METHODS

We conducted a prospective observational cohort study in the pediatric intensive care unit of Vietnam National Children's Hospital from October 2024 to June 2025. Children aged 1 month to under 18 years were included if RAI could be calculated within 24 h of admission. The primary outcome was severe AKI at 72 h, defined as KDIGO stage 2-3. Secondary outcomes included incident AKI, kidney replacement therapy, and PICU mortality. Predictive performance was evaluated using ROC analysis and multivariable logistic regression.

RESULTS

A total of 314 children were included. Severe AKI developed in 56 (17.8%) patients. RAI showed good discrimination for severe AKI (AUC 0.790; 95% CI 0.741-0.834), with sensitivity of 78.6% and specificity of 70.5% at a cutoff of ≥8. For incident AKI, the AUC was 0.752 (95% CI 0.643-0.861). RAI outperformed serum creatinine and fluid overload in predicting severe AKI. RAI ≥ 8 remained independently associated with severe AKI (adjusted OR 7.40; 95% CI 2.51-21.78; p < 0.001).

CONCLUSIONS

RAI showed acceptable performance for early prediction of severe AKI in critically ill children and may serve as a practical bedside risk stratification tool in resource-limited PICU settings.