Serum creatinine concentration in very-low-birth-weight infants from birth to 34-36 wk postmenstrual age.

BACKGROUND: Serum creatinine (s[Cr]) reference ranges for very-low-birth-weight (VLBW) infants must account for physiologic changes in the first months of life. METHODS: We retrospectively identified a sample of 218 appropriate-for-gestational age (GA) VLBW infants without risk factors for renal impairment, and classified into one of three GA groups: 25-27, 28-29, and 30-33 wk. We observed three phases of s[Cr] change (initial, decline, and equilibrium), whose characteristics varied by GA group. We used mixed-effects regression models to estimate mean and upper 95th prediction interval of s[Cr] for each GA group from birth to 34-36 wk post menstrual age (PMA). RESULTS: In phase I, s[Cr] increased after birth, then returned slowly to baseline. The duration of phase I and the magnitude of s[Cr] rise decreased with increasing GA. In phase II, s[Cr] declined abruptly at a rate that increased with GA. A gradual transition to phase III, a steady-state equilibrium with similar s[Cr] among GA groups, began at approximately 34-36 wk PMA. We constructed GA group-specific nomograms depicting s[Cr] behaviour across the three phases. CONCLUSION: The reference ranges derived from a sample of infants without risk factors for renal impairment provide a context for quantitative interpretation of s[Cr] trends in VLBW infants.

Reference values of urinary neutrophil gelatinase-associated lipocalin in very low birth weight infants.

In very low birth weight (VLBW) infants, acute renal impairment (ARI) is common, but there is no consensus about criteria for its diagnosis. Neutrophil gelatinase-associated lipocalin (NGAL) is an early and sensitive indicator of renal impairment in experimental animals, children, and adults. Urinary NGAL (UNGAL) is detectable in VLBW infants; however, there is no reference range in this population. The objective of this study is to define the reference range for UNGAL in VLBW infants with no risk factors for acute renal impairment. UNGAL concentration was determined in urine samples collected from day of life (DOL) 4 through DOL 30 in 50 newborns with uncomplicated clinical courses, selected from a total of 145 prospectively enrolled appropriate for gestational age inborn VLBW premature infants. The birth weight and gestational age ranges were 790-1490 g and 26-33 wk, respectively. The median, 95th and 99th percentiles, and range of pooled UNGAL values were 5 ng/mL, 50 ng/mL, 120 ng/mL, and 2-150 ng/mL, respectively. Greater variability and higher quantile levels of UNGAL were observed in females versus males. In conclusion, a reference range for UNGAL in VLBW infants, similar to that in children and adults, has been established.