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&gt;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

Cystatin C serum levels in term newborns along the neonatal period

INTRODUÇÃO: A cistatina C sérica apresenta boa correlação com o ritmo de filtração glomerular (RFG) e não é influenciada pela função renal materna, podendo ser um bom marcador da função renal, especialmente na 1ª semana de vida. Porém, não há valores normais definidos para o período neonatal. OBJETIVO: Determinar a evolução dos níveis séricos da cistatina C (Cis) em recém-nascidos (RN) de termo saudáveis ao longo do 1º mês de vida. MÉTODOS: Estudo prospectivo. Inclusão: idade gestacional (IG) entre 37 e 41 6/7 semanas; peso de nascimento adequado para a IG; Apgar 1º min > 7; mães sem insuficiência renal, hipertensão arterial ou uso de drogas que interferissem com a função renal do feto. Exclusão: má-formação major ou renal; ausência de diurese nas primeiras 12 horas de vida ou diurese no 2° ou 3° dia 10% até o 3º dia; pressão arterial elevada; insuficiência cardíaca ou renal, fototerapia, infecção, alteração da função tireoidiana ou uso de drogas vasoativas ou diuréticos. Dosagens laboratoriais: Cis (mg/L) por imunonefelometria e creatinina sérica (Cr) (mg/dL) pelo método de Jaffé, da mãe e do RN, no cordão umbilical (d0) e com 3 (d3), 7 (d7) e 28 (d28) dias. O clearance de creatinina foi estimado pela fórmula de Schwartz (mL/min/1,73m2). Comparação de médias pelo teste ANOVA one way para medidas repetidas e teste de Tukey. Análise de correlação pelo coeficiente de correlação de Pearson. Nível de significância=0,05. RESULTADOS: Preencheram os critérios de inclusão 35 RN e, destes, 14 foram excluídos. Foram analisados 21 RN. Mães: idade (média): 29,1 anos. Os RN apresentaram IG (mediana) de 39,4 sem e peso (média) de 3224 g; 57,1% eram do sexo masculino. A diurese (média) no 2° e no 3° dias foi 2,1 e 2,4 mL/kg/h, respectivamente, e a perda de peso máxima (média) foi 7,1% e ocorreu com 2 dias (mediana). Dos 21 RN, 17 (81%) receberam aleitamento materno exclusivo e 13 (61,9%) tiveram icterícia. Cis (média±dp): mãe: 1,00±0,20; RN: d0=1,70±0,26; d3=1,51±0,19; d7=1,54±0,15; d28=1,51±0,15. Cr (média±dp): mãe: 0,63±0,15; RN: d0=0,63±0,15; d3=0,48±0,16; d7=0,37±0,10; d28=0,26±0,05. Os valores de Cr não foram diferentes dos encontrados na literatura para RN de termo saudáveis. A Cr da mãe não foi diferente de d0, enquanto a Cis materna foi menor do que em d0 (p 7; mother without renal failure or drugs that could affect fetal GFR. Exclusion: malformations; hypertension; no diuresis in the first 12 hours of life or oliguria in the first three days; excessive weight loss until the third day; heart or kidney failure; thyroid dysfunction; use of diuretics, vasoactive drugs or any drug that could affect renal function. Cys (mg/L) and creatinine (Cr) (mg/dL) were determined in the mother (Mo) and in the NB at birth (d0), 3rd (d3), 7th (d7) and 28th (d28) days. Creatinine clearance was estimated in the NB using the Schwartz formula. Statistics: one way ANOVA and Pearsons correlation tests. Significance level=0.05. RESULTS: Data from 21 NB were obtained. Mothers: age (mean): 29.1 years. NB: gestational age (median): 39.4 weeks; birth weight (mean): 3224 g; 57.1% were male. Diuresis (mean) in the 2nd and 3rd days of life: 2.1±0.6 and 2.4±0.7 mL/kg/h, respectively. Maximum weight loss (mean): 7.1%; it occurred in the 2nd day (median). 81% of the NB were breastfed and 61.9% had jaundice. Cys (mean±sd): Mo: 1.00±0.20; NB: d0=1.70±0.26; d3=1.51±0.19; d7=1.54±0.15; d28=1.51±0.15. Cr (mean±sd): Mo: 0.63±0.15; NB: d0=0.63±0.15; d3=0.48±0.16; d7=0.37±0.10; d28=0.26±0.05. These Cr values are similar to those found in the literature for healthy term NB. Mo Cr was not different from d0 Cr, while Mo Cys was lower than d0 Cys (p<0.001). NB Cr decreased (d0xd3, p=0.007; d3xd7, p=0.002; d7xd28, p<0.001) along the time, while Cys decreased from d0 to d3 (p=0.004). Correlations were obtained between Mo Cr and Mo Cys, as well as d3 Cr and d3 Cys, d28 Cr and d28 Cys. CONCLUSIONS: At birth, NB Cys values were higher than Mo Cys values. NB Cys decreased from d0 to d3 and remained stable from d3 to d28. Mo Cys correlated with Mo Cr and NB Cys correlated with NB Cr at d3 and d28