title: Early postoperative serum cystatin C predicts severe acute kidney injury following cardiac surgery: a post-hoc analysis of a randomized controlled trial.
abstract: OBJECTIVE
  Acute kidney injury (AKI) after cardiac surgery procedures is associated with poor patient outcomes. Cystatin C as a marker for renal failure has been shown to be of prognostic value; however, a wide range of its predictive accuracy has been reported. The aim of the study was to evaluate whether the measurement of pre- and postoperative serum cystatin C improves the prediction of AKI.
  
  
  METHODS
  In a single-centre, prospective study of 70 patients (74 ± 9 ys; range 47-85 ys; 77% male), cystatin C was measured six times: (T1=preoperative, T2=start cardiopulmonary bypass (CPB), T3=20 min after CPB, T4=end of operation; T5=24 h postoperatively; T6=7d postoperatively). Predictive property, in terms of the need for renal replacement therapy (RRT), was analysed by receiver operating characteristics (ROC) statistics and described by the area under the curve (AUC).
  
  
  RESULTS
  With respect to RRT (n=8), serum cystatin C was significantly higher at the end of the operation (T4), 24 h postoperatively at T5 and at T6. The AUCs for preoperative T1 and intraoperative T2/3 cystatin C were <0.7 (95% CI, 0.47-0.85). The earliest significant predictive AUCs were found at the end of the operation (T4: p=0.03 95% CI 0.58-0.88 AUC 0.73) and 24 h postoperatively (T5: p=0.003 95% CI 0.74-0.96 AUC 0.85).
  
  
  CONCLUSIONS
  Early postoperative serum cystatin C increase appears to be a moderate biomarker in the prediction of AKI, whereas a preoperative and intraoperative cystatin C increase has only a limited diagnostic and predictive value.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Johann Wolfgang Goethe University, Theodor Stern Kai 7, Frankfurt am Main 60590, Germany. cardiac.surgeon@dr-kiessling.com.
authors.forename: Arndt-Holger
authors.initials: AH
authors.lastname: Kiessling
authors.forename: Juliane
authors.initials: J
authors.lastname: Dietz
authors.forename: Christian
authors.initials: C
authors.lastname: Reyher
authors.forename: Ulrich A
authors.initials: UA
authors.lastname: Stock
authors.forename: Andres
authors.initials: A
authors.lastname: Beiras-Fernandez
authors.forename: Anton
authors.initials: A
authors.lastname: Moritz
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D055316:Cystatin C / Q000097:blood*; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D055316:Cystatin C