Serum Cystatin C Is an Early Predictive Biomarker of Acute Kidney Injury after Pediatric Cardiopulmonary Bypass

Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB). Serum creatinine (SCr), the current standard, is an inadequate marker for AKI since a delay occurs before SCr rises. Biomarkers that are sensitive and rapidly measurable could allow early intervention and improve patient outcomes. We investigated the value of serum cystatin C as an early biomarker for AKI after pediatric CPB. We analyzed data from 374 prospectively enrolled children undergoing CPB. Serum samples were obtained before and at 2, 12, and 24 hours after CPB. Cystatin C was quantified by nephelometry. The primary outcome was AKI, defined as a > or =50% increase in SCr. Secondary outcomes included severity and duration of AKI, hospital length of stay, and mortality. A multivariable stepwise logistic regression analysis was used to assess predictors of AKI. One hundred nineteen patients (32%) developed AKI using SCr criteria. Serum cystatin C concentrations were significantly increased in AKI patients at 12 hours after CPB (P < 0.0001) and remained elevated at 24 hours (P < 0.0001). Maximal sensitivity and specificity for prediction of AKI occurred at a 12-hour cystatin C cut-off of 1.16 mg/L. The 12-hour cystatin C strongly correlated with severity and duration of AKI as well as length of hospital stay. In multivariable analysis, 12-hour cystatin C remained a powerful independent predictor of AKI. Serum cystatin C is an early predictive biomarker for AKI and its clinical outcomes after pediatric CPB.