Longitudinal study of Cystatin C in healthy term newborns

OBJECTIVE The purpose of this study was to determine the levels of Cystatin C in healthy term newborns in the first month of life. INTRODUCTION Cystatin C may be a suitable marker for determining the glomerular filtration rate because it is not affected by maternal renal function. METHODS Cohort study. Inclusion: term newborns with appropriate weight; mother without renal failure or drugs that could affect fetal glomerular filtration rate. Exclusion: malformations; hypertension or any condition that could affect glomerular filtration rate. Cystatin C (mg/L)and creatinine (rng/dl) were determined in the mother (Mo) and in the newborn at birth (Day-0), 3rd (Day-3), 7th(Day-7) and 28t>h(Day-28) days. STATISTICS one way ANOVA and Pearson's correlation tests. Sample size of 20 subjects for a = 5% and a power test = 80% (p<0.05). RESULTS Data from 21 newborns were obtained (mean + standard deviation): MoCystatin C=1.00 ± 0.20; Day-0 Cystatin C 1.70 ± 0.26; Day-3 Cystatin C = 1.51 ± 0.20; Day-7 Cystatin C = 1.54 ± 0.10; Day-28 Cystatin C = 1.51 ± 0.10. MoCystatin C was smaller than Day-0 Cystatin C (p < 0.001), while MoCreatinine was not different from Day-0 Creatinine. Cystatin C only decreased from Day-0 to Day-3 (p = 0.004) but newborns Creatinine decreased along the time. Correlations were obtained between MoCystatin C and MoCreatinine (p = 0.012), as well as Day-3 (p = 0.047) and Day-28 (p = 0.022) Cystatin C and Creatinine values. CONCLUSION Neonatal Cystatin C values were not affected by MoCystatin C and became stable from the 3rd day of life.