GFR Estimated From Cystatin C Versus Creatinine in Children Born Small for Gestational Age
Received 6 September 2007; accepted 12 February 2008. published online 06 May 2008.
Background
Low birth weight caused by intrauterine growth restriction may be a risk factor for renal impairment in the adult life.
Study Design
A cross-sectional study.
Setting & Participants
71 children aged 8 to 13 years living in the community of São Paulo, Brazil, were included in the study. Gestational age was within the normal range.
Predictors
Birth weight (range, 2,052 to 3,560 g) divided into quartiles: 2,500 g or less; 2,501 to 2,740 g; 2,741 to 3,000 g; and greater than 3,000 g. Birth weight ascertained by birth records in 43 and by recall in 28 participants.
Outcomes & Measurements
Cystatin C, creatinine, and glomerular filtration rate (GFR) estimated by equations using cystatin C (eGFRcys) or creatinine (eGFRcr).
Results
Overall, mean serum creatinine level was 0.8 ± 0.01 (SE) mg/dL (range, 0.7 to 1.1 mg/dL); mean plasma cystatin C level was 0.9 ± 0.02 mg/L (range, 0.5 to 1.6 mg/L), and eGFRcr and eGFRcys were 102.4 ± 2.16 (range, 66 to 140) and 91.8 ± 2.46 mL/min/1.73 m2 (range, 49 to 139 mL/min/1.73 m2), respectively. No differences were found for serum creatinine or eGFRcr values among the birth-weight quartiles. There was a significant linear trend of increasing cystatin C levels (decreasing eGFRcys) in the lower birth-weight quartile groups (P = 0.002 and P = 0.02, respectively). Systolic blood pressure correlated with plasma cystatin C level (r = 0.31; P = 0.008) and eGFRcys (r = −0.26; P = 0.028). Covariance analysis adjusting for age, sex, body mass index for age compared with standards of the National Center for Health Statistics and expressed as a z score, and systolic blood pressure showed that cystatin C values remained greater in the lowest than highest birth-weight quartile (1.01 ± 0.05 versus 0.83 ± 0.05 mg/L; P = 0.02).
Limitations
Ascertainment of birth weight by recall in some participants. Lack of measurement of microalbuminuria, absence of direct GFR measurement, and small sample size.
Conclusions
Lower birth weight is associated with higher levels of cystatin C but not creatinine in 8-13 yr. old children born full-term.
Department of Medicine, Division of Nephrology, Federal University of São Paulo, São Paulo, Brazil.
Address correspondence to Maria C.P. Franco, PhD, Federal University of São Paulo, Division of Nephrology, R. Botucatu, 740-São Paulo, SP, Brazil 04023-900.
ABSTRACT