BACKGROUND: The efficacy of urine neutrophil gelatinase-associated lipocalin (uNGAL) as an early acute kidney injury (AKI) biomarker in preterm neonates was evaluated.METHODS: Thirty-five preterm neonates were prospectively evaluated for serum creatinine (sCre)-documented AKI during the first 14 days of life. Urine samples were collected daily throughout the study period. Of the neonates evaluated, we analyzed 11 who developed AKI (cases) and an equal number of neonates without AKI (controls) matched for gestational and postnatal age (case-control study). uNGAL was measured on the day of AKI occurrence (day 0) and on the 2 days preceding the event (day -1 and day -2, respectively) using an enzyme-linked immunosorbent assay.RESULTS: Cases had significantly higher sCre levels than controls on day 0 (1.21 ± 0.48 vs. 0.83 ± 0.16 mg/dL, p =0.031) but not on days -1 and -2. Similarly, uNGAL levels (ng/mL) were significantly higher in cases than in controls only on day 0 (19.1 ± 3.5 vs. 13.3 ± 7.3, p=0.017) and not on days -1 (18.8 ± 3.4 vs. 16.3 ± 5.9, p=0.118) and -2 (19.3 ± 1.8 vs. 19.4 ± 0.8, p =0.979). The receiver operating characteristic curve analysis showed no significant ability of uNGAL to predict AKI on days -2 and -1.CONCLUSIONS: In this pilot study in preterm neonates, although uNGAL detected sCre-based AKI upon its documentation, it failed to predict its development 1-2 days earlier.