title: Cystatin C as a marker of acute kidney injury in the emergency department.
abstract: OBJECTIVE
  The diagnosis of acute kidney injury (AKI) is usually based on changes in serum creatinine, which is a poor marker of early renal dysfunction. The discriminative and predictive abilities of serum and urinary cystatin C were examined for the prediction of AKI.
  
  
  METHODS
  In this prospective cohort study, serum and urinary cystatin C were serially measured in a heterogeneous group of patients (n = 616) presenting to a tertiary care emergency department. The primary outcome was AKI, classified according to RIFLE and AKIN criteria. The secondary outcome was an adjudication based on clinical criteria to AKI, prerenal azotemia, chronic kidney disease (CKD), and normal kidney function.
  
  
  RESULTS
  Patients were adjudicated to have AKI in 21.1%, prerenal azotemia in 25.8%, CKD in 2.4%, and normal kidney function in 50.7%. For the diagnosis of AKI, the discriminatory ability of urinary creatinine and cystatin C was marginal. Both serum cystatin C and serum creatinine (at presentation and 6 hours later) showed high discriminatory ability for the diagnosis of AKI. However, only serum cystatin C attained a significant early predictive power (Hosmer-Lemeshow P value > 0.05). Serum cystatin C could differentiate between AKI and prerenal azotemia, but not between AKI and CKD.
  
  
  CONCLUSIONS
  Serum cystatin C is an early, predictive biomarker of AKI, which outperforms serum creatinine in the heterogeneous emergency department setting. However, neither biomarker discriminated between AKI and CKD. Additional biomarkers continue to be needed for improved specificity in the diagnosis of community-acquired AKI.
authors.affiliation: Department of Nephrology, Hospital Fernando Fonseca, Lisbon, Portugal.
authors.forename: Karina
authors.initials: K
authors.lastname: Soto
authors.forename: Silvia
authors.initials: S
authors.lastname: Coelho
authors.forename: Bruno
authors.initials: B
authors.lastname: Rodrigues
authors.forename: Henrique
authors.initials: H
authors.lastname: Martins
authors.forename: Francisca
authors.initials: F
authors.lastname: Frade
authors.forename: Stela
authors.initials: S
authors.lastname: Lopes
authors.forename: Luis
authors.initials: L
authors.lastname: Cunha
authors.forename: Ana Luisa
authors.initials: AL
authors.lastname: Papoila
authors.forename: Prasad
authors.initials: P
authors.lastname: Devarajan
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D000328:Adult; D000368:Aged; D053099:Azotemia / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016009:Chi-Square Distribution; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C / Q000097:blood* / Q000652:urine; D003937:Diagnosis, Differential; D042241:Early Diagnosis; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010343:Patient Admission; D011174:Portugal; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D003404:Creatinine