The significance of serum cystatin C accompanied by a normal serum creatinine level in pediatric patients with chronic kidney disease

Background: To evaluate the significance of serum cystatin C (Cys C) levels in pediatric patients with chronic kidney disease (CKD) diagnosed by renal biopsy and who show normal serum creatinine (Cr) levels. Methods: The patient group was composed of 167 males (M) and 119 females (F) with CKD enrolled from the Department of Pediatrics at Kyung Hee Medical Center from July 2009 to May 2010. The serum Cys C, Cr, and C-reactive protein (CRP) were tested using a chemical analyzer (Toshiba, Nasushiobara, Japan). Results: The mean age of the total patients was 11.72 years, and the mean body weight was 32.24 kg. The mean Cys C value was 0.84 mg/L, and 24 patients (3 Henoch-Schönlein purpura nephritis [HSPN], 3 IgA nephropathy [IgAN], 10 mesangial proliferative nephritis [MesPN], and 8 nephritic syndrome [NS]) showed increased Cys C levels (range: 1.0-1.6 mg/L). Conclusions: In this study, 95% of the patients showed only slightly increased Cys C levels (0.5~1.1 mg/L) from the upper normal limit of the reference range (0.9 mg/L). Therefore, we carefully suggest that mildly increased Cys C without increased Cr might not have clinical significance.