Urinary Cystatin C and Acute Kidney Injury After Cardiac Surgery

Background Acute kidney injury (AKI) is common after cardiac surgery and is associated with adverse patient outcomes. Urinary cystatin C (CysC) level is a biomarker of proximal tubule function and may increase earlier in AKI than serum creatinine level. Study Design Prospective cohort study. Settings & Participants The TRIBE AKI (Translational Research Investigating Biomarker Endpoints in AKI) Consortium prospectively enrolled 1,203 adults and 299 children and adolescents at 8 institutions in 2007-2009. Index Test Urinary CysC (in milligrams per liter) within the first 12 hours after surgery. Outcome Serum creatinine–based AKI was defined as AKI Network stage 1 (mild AKI) and doubling of serum creatinine from the preoperative value or need for dialysis during hospitalization (severe AKI). Other Measurements Analyses were adjusted for characteristics used clinically for AKI risk stratification, including age, sex, race, estimated glomerular filtration rate, diabetes, hypertension, heart failure, nonelective surgery, cardiac catheterization within 72 hours, type of surgery, myocardial infarction, and cardiopulmonary bypass time longer than 120 minutes. Results Urinary CysC level measured in the early postoperative period (0-6 and 6-12 hours postoperatively) correlated with both mild and severe AKI in adults and children. However, after analyses were adjusted for other factors, the effect was attenuated for both forms of AKI in both cohorts. Limitations Limited numbers of patients with severe AKI and in-hospital dialysis treatment. Conclusions Urinary CysC values are not associated significantly with the development of AKI after cardiac surgery in adults and children.