Integration of Urinary Neutrophil Gelatinase-associated Lipocalin with the Renal Angina Index to Predict Subsequent Severe Acute Kidney Injury in Critically Ill Children: A Diagnostic Accuracy Study

The primary objective of this study was to determine the performance of the renal angina index (RAI) in predicting subsequent severe acute kidney injury (AKI) on day 3 of admission and whether integrating urinary neutrophil gelatinase-associated lipocalin (NGAL) with RAI would lead to improved prediction of AKI. This was a prospective observational study conducted in the pediatric intensive care unit (PICU) of a tertiary care hospital involving 170 children meeting the inclusion criteria. The RAI was assessed within 24 h of admission to the PICU. Positivity for renal angina was considered RAI ≥8. Urine samples were collected for all enrolled patients within the first 24 h and on day 3 of the PICU stay. NGAL was assayed using human-specific enzyme-linked immunosorbent assay. The overall incidence of AKI was 18.2%. Out of 170 children, 31 (18.2%) were RAI-positive on day 0. A higher proportion of patients in the RAI-positive group developed AKI on day 3 compared with the RAI-negative group (83.9% vs. 3.6%, P <0.001). Those who were RAI-positive on day 0 had a sensitivity, specificity, positive predictive value (PPV), and negative predictive value of 83.8%, 96.4%, 83.8%, and 96.4%, respectively, for predicting severe AKI on day 3. Incorporating urinary NGAL improved the specificity and PPV to 97.8% and 85.7%, respectively. Assessing the RAI is simple and useful for predicting severe AKI in critically ill children. The addition of urinary NGAL to the RAI optimizes its use for identifying patients at risk of subsequent severe AKI.