Reference values of umbilical cord and third-day cystatin C levels for determining glomerular filtration rates in newborns.

The aim of this study was to determine reference values for serum cystatin C at, and 3 days after, birth, and to determine if the concentration was influenced by gender, gestational age or bilirubin level. Umbilical cord and peripheral venous blood was taken, and serum cystatin C, creatinine, and total and direct bilirubin levels were measured. The mean concentration of cystatin C was not significantly different between cord blood and blood taken on day 3 (1.36 +/- 0.35 mg/l and 1.35 +/- 0.33 mg/l, respectively). Comparison of subgroups, divided by gender, duration of gestation and bilirubin levels, using the Mann-Whitney U-test and Wilcoxon analysis, showed no effect of these parameters on cystatin C levels.