Reference Range of Urinary Neutrophil Gelatinase-Associated Lipocalin in Very Low-Birth-Weight Infants: Preliminary Data

We sought to determine the reference range for urinary neutrophil gelatinase-associated lipocalin (UNGAL) in very low-birth-weight (VLBW) infants with uncomplicated clinical courses. Samples of urine from 53 VLBW infants between 3 and 28 days of life were prospectively collected weekly for measurement of UNGAL. A subset of 22 infants with uncomplicated medical courses without risk factors for renal impairment was selected for study. Mean +/- standard deviation and range for birth weight and gestational age of study infants were 1156 +/- 191, 790 to 1440 g and 29 +/- 2, 27 to 33 weeks, respectively. The 95th and 99th percentiles for UNGAL concentration from this group of infants were 25 ng/mL and 75 ng/mL, respectively. Bootstrapped mean 95th and 99th percentile values and their standard errors and 95 percent confidence intervals in ng/mL were 33.1 +/- 13.0 (7.7, 58.6) and 67.5 +/- 15.1 (37.9, 97.1), respectively. These values fan within the adult reference range. UNGAL values were stable across the ranges of gestational and postnatal age of the study infants. A preliminary reference range for UNGAL in VLBW infants has been established. Further investigation with more frequent urine collections in a larger population of VLBW infants that includes those with birth weights < 750 g and gestational ages < 27 weeks is necessary to confirm this reference range.