Reference Interval for Serum Cystatin C in Children

Abstract

Serum creatinine and creatinine clearance are widely used as measures of glomerular filtration rate (GFR) in clinical medicine. Unfortunately, serum creatinine concentrations are not determined only by glomerular filtration (1). Alteration in renal handling and metabolism of creatinine and methodological interferences in its measurement may influence the concentrations of serum creatinine (2). Creatinine production is proportional to muscle mass (2). In children, the muscle mass increases significantly with linear growth, and serum creatinine concentrations have to be adjusted for body height and body size to reflect the renal function (3)(4). Cystatin C, a nonglycosylated low molecular weight protein ( M r 13.359) (5), is a proteinase inhibitor involved in the intracellular catabolism of proteins (6). Unlike creatinine, cystatin C is produced in all investigated nucleated cells at a constant rate, freely filtered in the renal glomeruli and almost completely reabsorbed and catabolized in the renal proximal tubular cells (7)(8). Recent studies have indicated that serum cystatin C can be used as an endogenous marker of GFR in adults (9)(10) and is a promising marker in children (11)(12)(13). The aim of the study was to establish a reference interval for serum cystatin C in children without evidence of kidney disease. One hundred and thirty-seven children (79 boys and 58 girls) of ages between 7 days and 14.1 years (3.2 ± 3.5 years; mean ± SD) with body weight >1.5 kg and without clinical evidence of kidney diseases were included in the study (Table 1⇓ ). Twenty-nine children had pneumonia, 25 viral infections, 32 other infectious diseases, 23 bronchial asthma, and 28 other noninfectious diseases. The children’s parents gave their informed consents according to the Declaration of Helsinki, and the study was approved by the local committee of ethics. During a …