Objectives: We aimed to evaluate the value of serum cystatin C for detection of acute kidney injury and pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease categories in critically ill children and to investigate whether serum cystatin C was associated with outcome.
Design: Prospective cohort study.
Setting: PICU of a tertiary-care university hospital.
Patients: A heterogeneous population of critically ill children.
Interventions: None.
Measurements and main results: Blood and 24-hour urine samples were collected daily over the first 2 days after PICU admission for measurement of serum cystatin C, serum creatinine, and creatinine clearance. Acute kidney injury was classified by pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease criteria. One hundred twenty-two children were prospectively enrolled; 40 (32.8%) developed acute kidney injury. Serum cystatin C was higher in patients with acute kidney injury compared with those who did not develop acute kidney injury at PICU admission (median, 0.90 mg/L vs 0.51 mg/L) and on the first (1.12 mg/L vs 0.57 mg/L) and second PICU days (1.15 mg/L vs 0.58 mg/L). Serum creatinine was higher in acute kidney injury group only on the first (0.50 mg/dL vs 0.40 mg/dL) and second PICU days (0.60 mg/dL vs 0.40 mg/dL). Serum cystatin C was increasingly higher according to acute kidney injury severity (Failure > Injury > Risk). Area under the receiver operating characteristic curve of cystatin C for acute kidney injury detection was 0.89. Serum cystatin C greater than 0.70 mg/L was associated with longer length of PICU stay (adjusted hazard ratio, 1.64) and prolonged duration of mechanical ventilation (adjusted hazard ratio, 1.82).
Conclusions: Cystatin C is an early and accurate biomarker for acute kidney injury and pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease categories, and it is associated with adverse clinical outcomes in a heterogeneous population of critically ill children.