Cystatin C Intrapatient Variability in Children with Chronic Kidney Disease Is Less than Serum Creatinine

Abstract

Serum Cystatin C (CysC) (1) is a promising new marker for glomerular filtration rate (GFR) in children(2) because of its independence from height and sex(3). Although the superiority of CysC over serum creatinine (SCr) for the detection of impaired GFR has been demonstrated in a metaanalysis(4), widespread clinical use of the marker remains limited because of previously reported substantial intrapatient variability of CysC in healthy volunteers(5). After obtaining approval from the Institutional Review Board, we analyzed the analytical imprecision of CysC (nephelometric Dade Behring assay; BN Prospec platform) and SCr (enzymatic assay; Ortho Clinical Diagnostics) as well as interpatient variability in 38 children [19 males; mean (SD) age, 10.1 (4.95) years] who underwent 99mTc diethylenetriaminepentaacetic acid GFR renal scans and had a normal (i.e., within reference values) GFR between 90 and 135 mL · min−1 · (1.73 m …