Early detection of acute kidney injury by serum cystatin C in critically ill children

We prospectively evaluated whether serum cystatin C (CysC) detected acute kidney injury (AKI) earlier than basal serum creatinine (Cr). In 107 pediatric patients at high risk of developing AKI, serum Cr and serum CysC were measured upon admission. Baseline estimated creatinine clearance (eCCl) was calculated using a CysC-based glomerular filtration rate (GFR) equation from a serum Cr measured at the pediatric intensive care unit (PICU) entrance. The median age was 10 months (interquartile range, 3-36 months). Serum Cr, serum CysC, and eCCl (mean +/- standard deviation [range]) were 0.5 +/- 0.18 mg/dl (0.2-1.1 mg/dl), 0.53 +/- 0.78 (0.01-3.7 mg/l), and 72.55 +/- A 28.72 (20.6-176.2) ml/min per 1.73 m(2), respectively. The serum CysC level in patients with AKI was significantly higher than children with normal renal function (p < 0.001). The values for the cut-off point, sensitivity, specificity, and the area under curve (AUC) were determined for CysC as 0.6 mg/l, 73.9 %, 78.9 %, and 0.92 [95 % confidence interval (0.82-1)], respectively, and for Cr the values were 0.4 mg/dl, 68 %, 46.2 %, and 0.39, [95 % confidence interval (0.24-0.54)], respectively. The receiver operating characteristics (ROC) curve analysis revealed that CysC had a significantly higher diagnostic accuracy than eCCl (p < 0.001). Our results identify that the sensitivity of serum CysC for detecting AKI is higher than that of serum Cr in a heterogeneous pediatric intensive care unit (PICU) population.