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June 27, 2026

Urinary Neutrophil Gelatinase-Associated Lipocalin and Serum Cystatin C as Early Biomarkers of Acute Kidney Injury in Critically Ill Children: Single-Center PICU Cohort, 2024–2025

AFAna Rita FradiqueHospitais da Universidade de Coimbra MFMariana FerreiraUniversity of Coimbra ARAlexandra Costa RodriguesHospitais da Universidade de Coimbra

Key Points

This study aims to evaluate urinary neutrophil gelatinase-associated lipocalin and serum cystatin C as early biomarkers for acute kidney injury in critically ill children.
Single-center cohort study conducted in a pediatric intensive care unit (PICU).
Analyzed 75 patients over 10 months, focusing on biomarkers and clinical parameters associated with AKI.
Measured uNGAL and Cys-C levels on days 1-3 to assess their relationship with AKI development.
AKI developed in 22 patients (29.3%); uNGAL showed significant elevation on days 1, 2, and 3 (p < 0.001, p = 0.003, p = 0.013 respectively).
Cystatin C was elevated on day 1 only (p = 0.013); good-to-excellent discrimination for AKI with uNGAL (AUC 0.847) and blood urea nitrogen (AUC 0.848).
Diagnostic uncertainty remained with a 29.3% pretest probability of AKI, rising to 73.1% posttest with uNGAL >87 ng/mL.

Abstract

Introduction: We have explored the use of early biomarkers for the timely identification of acute kidney injury (AKI) in critically ill children. Design: Single-center cohort study. Setting: Tertiary medical-surgical PICU in Coimbra, Portugal. Patients: Pediatric patients admitted for longer than 48 hours over a 10-month period during 2024–2025. Interventions: None. Measurements and Results: Among 75 patients (55.3% male; median age 3.9 yr), 22 patients (29.3%) developed AKI (defined by Kidney Disease Improving Global Outcomes criteria) on day 1. On comparing those with or without AKI, urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels were elevated on day 1 ( p < 0.001), day 2 ( p = 0.003), and day 3 ( p = 0.013) in AKI patients. Cystatin-C (Cys-C) was only increased on day 1 ( p = 0.013). Shock ( p < 0.001) and vasoactive drug use ( p = 0.007) were more commonly present in AKI patients, who also had lower albumin ( p = 0.012), platelets ( p = 0.001), and bicarbonate level ( p = 0.032). AKI patients also had higher C-reactive protein (CRP; p = 0.018), procalcitonin ( p = 0.002), and lactate concentration ( p = 0.022). Shock and CRP were associated with greater odds (presented as odds ratio OR with 95% CI) of AKI, respectively as: OR, 6.10 (95% CI, 1.50–16.52); p = 0.002; and OR, 1.07 (95% CI, 1.00–1.12); p = 0.022; as well as day 1 Renal Angina Index (RAI; OR, 1.10 95% CI, 1.03–1.17; p = 0.005). On day 1, the discrimination performance (using the area under the receiver operating characteristic curve AUC) for AKI was good-to-excellent for, respectively: uNGAL, 0.847 (95% CI, 0.74–0.96); p value of less than 0.001; and blood urea nitrogen, 0.848 (95% CI, 0.75–0.95); p value of less than 0.001. Regarding uNGAL, the pretest probability of AKI was 29.3%, and the posttest probability of AKI on finding a uNGAL greater than 87 ng/mL rose to 73.1%, which leaves significant diagnostic uncertainty. Also, the day 1 RAI was an acceptable to good discriminator of the severity of AKI in those identified with AKI: AUC, 0.796 (95% CI, 0.60–0.99); p = 0.019. Conclusions: In our PICU cohort, day 1 uNGAL level greater than 87 ng/mL has good-to-excellent discriminative capacity in identifying AKI, but the diagnostic uncertainty of AKI remains.

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