title: Serum and urine cystatin C are poor biomarkers for acute kidney injury and renal replacement therapy.
abstract: OBJECTIVE
  To evaluate whether cystatin C in serum (sCyC) and urine (uCyC) can predict early acute kidney injury (AKI) in a mixed heterogeneous intensive care unit (ICU), and also whether these biomarkers can predict the need for renal replacement therapy (RRT).
  
  
  METHODS
  Multicenter prospective observational cohort study in patients ≥18 years old and with expected ICU stay ≥72 h. The RIFLE class for AKI was calculated daily, while sCyC and uCyC were determined on days 0, 1, and alternate days until ICU discharge. Test characteristics were calculated to assess the diagnostic performance of CyC.
  
  
  RESULTS
  One hundred fifty-one patients were studied, and three groups were defined: group 0 (N = 60), non-AKI; group 1 (N = 35), AKI after admission; and group 2 (N = 56), AKI at admission. We compared the two days prior to developing AKI from group 1 with the first two study days from group 0. On Day -2, median sCyC was significantly higher (0.93 versus 0.80 mg/L, P = 0.01), but not on Day -1 (0.98 versus 0.86 mg/L, P = 0.08). The diagnostic performance for sCyC was fair on Day -2 [area under the curve (AUC) 0.72] and poor on Day -1 (AUC 0.62). Urinary CyC had no diagnostic value on either of the two days prior to AKI (AUC <0.50). RRT was started in 14 patients with AKI; sCyC and uCyC determined on Day 0 were poor predictors for the need for RRT (AUC ≤0.66).
  
  
  CONCLUSIONS
  In this study, sCyC and uCyC were poor biomarkers for prediction of AKI and the need for RRT.
authors.affiliation: Department of Anesthesiology, Tergooi Hospitals, location Blaricum, Blaricum, The Netherlands.
authors.forename: Annick A N M
authors.initials: AA
authors.lastname: Royakkers
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Korevaar
authors.forename: Jeroen D E
authors.initials: JD
authors.lastname: van Suijlen
authors.forename: Lieuwe S
authors.initials: LS
authors.lastname: Hofstra
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kuiper
authors.forename: Peter E
authors.initials: PE
authors.lastname: Spronk
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Schultz
authors.forename: Catherine S C
authors.initials: CS
authors.lastname: Bouman
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000628:therapy* / Q000652:urine; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015331:Cohort Studies; D055316:Cystatin C / Q000097:blood* / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020380:Needs Assessment; D017582:Renal Replacement Therapy
chemical_list: D015415:Biomarkers; D055316:Cystatin C