Background: Neutrophil gelatinase-associated lipocalin (NGAL) has been suggested as the most promising biomarker of acute kidney injury. However, there are no reliable data on analytical sensitivity and reference limits of urinary NGAL (uNGAL) assay in pediatric age. The aim of the present study is to evaluate the analytical sensitivity and the reference range of uNGAL measured in urine specimens of pediatric age with the fully automated platform ARCHITECT i1000.
Methods: A total of 333 urine samples were collected from 25 healthy newborns (16 males and 9 females; age 1-4 days) and 308 children (150 males and 147 females; mean age 80.7 months, range 0.63-248 months) and assayed for uNGAL by two different Italian centers (Department of Laboratory Medicine of the Fondazione Toscana G. Monasterio of Pisa and Massa and the Clinical Pathology Laboratory Unit of Istituto Giannina Gaslini of Genova).
Results: The calculated limits of blank (LOB) and detection (LOD) values were 0.5 ng/mL and 0.95 ng/mL, respectively. The distribution of uNGAL values approximated a log-normal distribution (median 5.2 ng/mL, interquartile range 2.5-12.8 ng/mL, 99th percentile 117.6 ng/mL). uNGAL values of the 25 neonates were significantly higher than those of 308 children (neonates: mean 44.2 ng/mL, median 30.3 ng/mL, range 5.2-137.4 ng/mL; children: mean 10.2 ng/mL, median 4.6 ng/mL, range 0.2-146.7 ng/mL; p<0.0001).
Conclusions: uNGAL assay shows a good analytical sensitivity and imprecision, which allows the measurement of uNGAL values around the cut-off value (i.e., 117.6 ng/mL) with an imprecision <5 CV%. The distribution of uNGAL values in pediatric age approximates a log-normal distribution, with values which are higher in neonates compared to children.