title: Serum cystatin C in elderly cardiac surgery patients.
abstract: BACKGROUND
  Elderly cardiac surgery patients are more prone to develop postoperative acute kidney injury (AKI). The common clinical glomerular filtration marker, plasma creatinine, is considered to be inadequate to discover AKI in its early stage. The aim of this study was to determine if serum cystatin C can detect mild renal failure earlier than plasma creatinine.
  
  
  METHODS
  From 110 cardiac surgery patients aged 70 or greater years, serum cystatin C and plasma creatinine samples were collected preoperatively and on postoperative days 1 to 5. Their urine output, creatinine, and estimated glomerular filtration rate were calculated and AKI was determined by the risk-injury-failure-loss-end-stage kidney disease criteria (RIFLE). The correlation of plasma creatinine and serum cystatin C to AKI was calculated.
  
  
  RESULTS
  After cardiac surgery, 62 of the 110 patients (56.4%) developed AKI according to the RIFLE classification. In this group, both serum cystatin C and plasma creatinine peaked on postoperative day 3. Cystatin C and creatinine correlated equally with AKI at different time points calculated with receiver operating characteristic curves. On postoperative day 1 the area under the curve (AUC) for creatinine was 0.66 (0.55 to 0.76) and for cystatin C 0.71 (0.61 to 0.81); Delta AUC 0.05 (0.01 to 0.12), p = 0.11. On postoperative day 2 the AUC for creatinine was 0.74 (0.64 to 0.83) and for cystatin was C 0.77 (0.68 to 0.86); Delta AUC -0.03 (-0.09 to 0.03), p = 0.32.
  
  
  CONCLUSIONS
  Elderly cardiac surgery patients have a high incidence of AKI, as defined by the RIFLE criteria. After cardiac surgery serum cystatin C and plasma creatinine detected AKI similarly.
authors.affiliation: Department of Anesthesia and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland. anne.ristikankare@hus.fi
authors.forename: Anne
authors.initials: A
authors.lastname: Ristikankare
authors.forename: Reino
authors.initials: R
authors.lastname: Pöyhiä
authors.forename: Anne
authors.initials: A
authors.lastname: Kuitunen
authors.forename: Markus
authors.initials: M
authors.lastname: Skrifvars
authors.forename: Pekka
authors.initials: P
authors.lastname: Hämmäinen
authors.forename: Markku
authors.initials: M
authors.lastname: Salmenperä
authors.forename: Raili
authors.initials: R
authors.lastname: Suojaranta-Ylinen
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis* / Q000209:etiology; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests; D008297:Male
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine