Cystatin C serum concentrations underestimate glomerular filtration rate in renal transplant recipients.
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Biomedical subjects
M Domanetzki
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Reference values for cystatin C serum concentrations in children.
Cystatin C, a low molecular weight protein, is a new endogenous marker of renal function whose serum concentration correlates better with glomerular filtration rate than creatinine. The aim of the present study was to define a reference interval for cystatin C concentrations in children. Cystatin C was measured by an immunoturbidimetric assay in sera obtained from 258 children (93 girls, 165 boys, median age 6.29 years, range 1 day to 18 years) without evidence of kidney disease. The reference interval was calculated non-parametrically using the 2.5th and 97.5th percentiles. For comparison, creatinine was measured in the same samples. The cystatin C concentration was highest on the first days of life (range 1.64-2.59 mg/l) with a rapid decrease during the first 4 months. Beyond the 1st year, the cystatin C concentration was constant, with a reference interval of 0.7-1.38 mg/l. In contrast, serum creatinine concentrations steadily increased with age until adulthood. Compared with creatinine, cystatin C facilitates the recognition of abnormal renal function in children as its reference range is constant beyond the 1st year of life. The higher levels of cystatin C in the 1st year of life probably reflect the low glomerular filtration rate of neonates and infants.
Adolescent↗
Cystatin C--a new marker of glomerular filtration rate in children independent of age and height.
OBJECTIVES: Serum creatinine is the most common endogenous marker of renal function. The proportionality between creatinine production and muscle mass requires adjustment for height and body composition. The low molecular weight protein cystatin C is produced by all nucleated cells and eliminated by glomerular filtration. Therefore, cystatin C was studied as an alternative marker of glomerular filtration rate (GFR) in children. METHODS: Cystatin C and creatinine were measured in sera from inulin clearance (CIn) examinations performed in 184 children aged 0.24 to 17.96 years. CIn ranged from 7 to 209 mL/min/1.73 m (median, 77). RESULTS: The reciprocal of cystatin C correlated better with CIn (r = 0.88) than the reciprocal of creatinine (r = 0.72). Stepwise regression analysis identified no covariates for the correlation between cystatin C and CIn, whereas height was a covariate for creatinine. Using an estimate of GFR from serum creatinine and height, correlation with CIn was similar to cystatin C, but female gender and dystrophy were associated with an overestimation of GFR. Diagnostic accuracy in the identification of reduced GFR measured as area under the receiver-operating characteristic plot was 0.970 +/- 0.135 (mean +/- SE) for cystatin C and 0.894 +/- 0.131 for creatinine (NS). A cutoff cystatin C concentration of 1.39 mg/L had 90% sensitivity and 86% specificity for detecting abnormal GFR. CONCLUSION: Unlike creatinine, serum cystatin C reflects renal function in children independent of age, gender, height, and body composition.
Adolescent↗