title: Cystatin C in acute kidney injury diagnosis: early biomarker or alternative to serum creatinine?
abstract: BACKGROUND
  Early acute kidney injury (AKI) diagnosis is needed to pursue treatment trials. We evaluated cystatin C (CysC) as an early biomarker of serum creatinine (SCr)-AKI and an alternative to define AKI.
  
  
  METHODS
  We studied 160 non-cardiac children in the intensive care unit (ICU). We measured daily CysC and SCr. AKI was staged by KDIGO (Kidney Disease: Improving Global Outcomes) guidelines using SCr and CysC (CysC-AKI). We calculated area under the curve (AUC) for (1) neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and urine CysC to diagnose SCr- and CysC-AKI; and (2) for CysC to diagnose SCr-AKI. We evaluated AKI associations with length of stay and ventilation duration.
  
  
  RESULTS
  We found that 44 % of patients developed SCr-AKI; 32 % developed CysC-AKI. Early ICU NGAL was most diagnostic of CysC-AKI (AUC 0.69, 95% CI 0.54-0.84); IL-18 was most diagnostic for SCr-AKI (AUC 0.69 95% CI 0.55-0.82). Combining SCr and CysC-AKI definition led to higher biomarker diagnostic AUC's. CysC-AKI was not more strongly associated with clinical outcomes. Early ICU CysC predicted SCr-AKI development (AUC 0.70, 95 % CI 0.53-0.89).
  
  
  CONCLUSIONS
  Our findings do not support replacing SCr by CysC to define AKI. Early ICU CysC predicts SCr-AKI development and combined SCr-CysC-AKI definition leads to stronger AKI biomarker associations.
authors.affiliation: Department of Pediatrics, McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Paola
authors.initials: P
authors.lastname: Lagos-Arevalo
authors.forename: Ana
authors.initials: A
authors.lastname: Palijan
authors.forename: Laura
authors.initials: L
authors.lastname: Vertullo
authors.forename: Prasad
authors.initials: P
authors.lastname: Devarajan
authors.forename: Michael R
authors.initials: MR
authors.lastname: Bennett
authors.forename: Venkata
authors.initials: V
authors.lastname: Sabbisetti
authors.forename: Joseph V
authors.initials: JV
authors.lastname: Bonventre
authors.forename: Qing
authors.initials: Q
authors.lastname: Ma
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Gottesman
authors.forename: Michael
authors.initials: M
authors.lastname: Zappitelli
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000175:diagnosis*; D000293:Adolescent; D015415:Biomarkers / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D006801:Humans; D007223:Infant; D015278:Intensive Care Units, Pediatric; D008297:Male; D011446:Prospective Studies
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine