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

Background and objectives: 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. Design, setting, participants, & measurements: 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 >= 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. Results: 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. Conclusion: Serum cystatin C is an early predictive biomarker for AKI and its clinical outcomes after pediatric CPB. Clin J Am Soc Nephrol 5: 1552-1557, 2010. doi: 10.2215/CJN.02040310