Urinary neutrophil gelatinase-associated lipocalin concentration: a baseline study for establishing reference ranges in preterm neonates

Abstract Background Acute kidney injury (AKI) affects up to 48% of extremely preterm neonates and is associated with significant morbidity and mortality. However, AKI diagnosis remains challenging in this population due to limitations of traditional markers like serum creatinine (Cr) and urine output. Urinary neutrophil gelatinase-associated lipocalin (uNGAL) has emerged as a promising biomarker for early AKI detection, but its clinical utility is hindered by a lack of normative reference ranges in preterm infants. Objective To characterize baseline uNGAL concentrations during the first postnatal week in preterm neonates without AKI and evaluate associations with gestational age (GA) at birth, birth weight (BW), and sex. Methods We conducted a cohort study of 100 neonates <32 weeks’ gestation without AKI, necrotizing enterocolitis, sepsis, or urinary tract infection. uNGAL and uNGAL/uCr ratios were measured and analyzed by GA, birth weight, and sex. Results Baseline uNGAL concentrations vary significantly by gestational age at birth, birth weight, and sex in preterm neonates during the first postnatal week. Conclusions Baseline uNGAL varies significantly with GA, BW, and sex in preterm neonates. These findings support the development of gestational age– and sex-specific normative reference ranges to improve the interpretation and diagnostic utility of uNGAL for neonatal AKI.