Plasma Cystatin C and Acute Kidney Injury after Cardiopulmonary Bypass

Background and objectives: Little is known about the performance of plasma cystatin C (CysC) in patients undergoing cardiopulmonary bypass (CPB) and its utility in the early diagnosis of acute kidney injury (AKI). In this post hoc analysis, the goal was to determine whether plasma cystatin C, measured 2 hours after the conclusion of CPB, is a reliable marker of AKI. Design, setting, participants, & measurements: Plasma CysC was measured in 150 patients undergoing CPB at the following times: preoperatively, 2 hours after the conclusion of CPB, postoperative day 1, and postoperative day 2. Plasma CysC levels were related to the development of AKI as defined by an increase in serum creatinine of >= 50% or >= 0.3 mg/dl from baseline up to 3 days postoperative. Mixed linear models were used to evaluate the relationship of serial plasma CysC values with AKI. The discriminatory capacity of plasma CysC was estimated using receiver operating characteristic curves. Logistic regression was utilized to assess the adjusted relationship between plasma CysC and subsequent AKI. Results: AKI developed in 47 (31.3%) patients. Plasma CysC was higher at all times among patients who developed AKI compared with those who did not (P < 0.0001). The discriminatory capacity of plasma CysC measured preoperatively and 2 hours after the conclusion of CPB was modest. Conclusions: Serial measures of plasma CysC are highly correlated with the development of AKI. However, the discriminatory capacity of plasma CysC as an early marker of AKI remains limited. Clin J Am Soc Nephrol 5: 1373-1379, 2010. doi: 10.2215/CJN.06350909