Renal angina index in the prediction of acute kidney injury in critically ill children

Abstract

Background: Renal Angina Index (RAI) was recently proposed as a tool to identify patients at high risk for severe acute kidney injury (AKI) by integrating baseline, contextual, and clinical evidence of renal injury and to optimize biomarker utility in intensive care units. Methods: In this unicentric prospective observational study, we estimated RAI at admission in 285 critically ill patients, aged 1 month to 18 years, and evaluated the utility of renal angina (RAI ≥8) in identifying patients with severe or any AKI on day 3 and day 7. The relationship between RAI and need for renal replacement therapy (RRT) and duration of mechanical ventilation and hospital stay was also examined. Results: Renal angina was present in 49.4% of 285 patients. Severe AKI, observed in 29 (10.2%) patients on day 3 and 13.2% of 144 patients followed to day 7, had an incidence of 1.1 (0.8–1.6) episodes per 100 person-days. Thirty-six (12.6%) patients required RRT. RAI satisfactorily identified patients at risk of severe AKI on days 3 (area under the curve [AUC]: 0.82; 95% confidence interval [CI]: 0.73–0.90) and 7 (AUC: 0.73; 95% CI: 0.62–0.84), was more useful than Pediatric Index of Mortality in such discrimination, and correlated with duration of mechanical ventilation and hospital stay. However, RAI thresholds ≥12 or ≥20 had higher specificity, Youden index, and positive predictive value than that of RAI ≥8 in discriminating severe AKI on day 3 or 7 and distinguished between patients with and without need for RRT. Conclusions: RAI usefully predicts the development of subsequent severe AKI on days 3 and 7, and is associated with duration of mechanical ventilation and hospital stay. A higher RAI threshold (≥12 or ≥20) is more discriminatory than RAI ≥8.