GFR Estimated From Cystatin C Versus Creatinine in Children Born Small for Gestational Age

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 (eGFR_cys) or creatinine (eGFR_cr).

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 eGFR_cr and eGFR_cys 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 eGFR_cr values among the birth-weight quartiles. There was a significant linear trend of increasing cystatin C levels (decreasing eGFR_cys) 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 eGFR_cys (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.

Index Words: Intrauterine growth restriction, cystatin C, glomerular filtration rate, birth weight