title: Urinary cystatin C as an early biomarker of acute kidney injury after open and endovascular abdominal aortic aneurysm repair.
abstract: BACKGROUND
  Acute kidney injury (AKI) after open repair (OR) and endovascular repair (EVAR) of abdominal aortic aneurysm (AAA) is associated with increased mortality and hospital costs. Early detection of AKI is critical to prevent its progression. Recent findings demonstrate that elevated levels of urinary cystatin C (uCysC) may reflect tubular dysfunction. We prospectively evaluated whether uCysC can detect renal dysfunction earlier than serum creatinine (sCr).
  
  
  METHODS
  In a prospective study, 126 consecutive patients (mean age ± SD, 69.1 ± 8.66 years) with AAA (EVAR = 87, OR = 39) were enrolled. sCr and uCysC were measured preoperatively (baseline) and at 6, 24, and 48 hr postoperatively. A final measurement was made on day 5. AKI was defined according to Acute Kidney Injury Network criteria.
  
  
  RESULTS
  The incidence of AKI was significantly higher (χ(2) test, P < 0.05) in the OR group (n = 13, 33%) than in the EVAR group (n = 15, 17%). The baseline median (interquartile range) value of uCysC was significantly higher (t-test, P < 0.05) in patients of both groups (OR-EVAR) who developed AKI from those who did not (OR/AKI group: 0.06 [0.02-0.12] mg/L, EVAR/AKI group: 0.08 [0.05-0.11] mg/L versus no-AKI subjects: 0.04 [0.02-0.07] mg/L). Subsequent analysis showed that at 6 hr postoperatively, the patients who developed AKI increased their uCysC levels significantly from baseline (OR/AKI group: 0.58 [0.42-0.70] mg/L, EVAR/AKI group: 0.59 [0.30-1.07] mg/L). The median value of uCysC in AKI patients increased at 24 hr (OR/AKI group: 1.37 [0.78-3.40] mg/L, EVAR/AKI group: 2.11 [0.70-2.42] mg/L) and peaked at 48 hr (OR/AKI group: 6.16 [1.74-10.73] mg/L, EVAR/AKI group: 2.57 [1.21-7.40] mg/L), while no increase was observed among those who did not develop AKI at the same time points (0.06 [0.04-0.14] vs. 0.08 [0.04-0.19] mg/L). The diagnostic accuracy of uCysC at 6 hr post-surgery was excellent (area under the curve - receiver-operating characteristic [AUC-ROC] = 0.968), significantly higher than sCr (AUC-ROC = 0.844) and a cutoff value set at 0.30 mg/L can diagnose AKI with a sensitivity of 85.71% and a specificity of 98.97%.
  
  
  CONCLUSIONS
  uCysC is superior to sCr in the early diagnosis of AKI following open and endovascular AAA repair.
authors.affiliation: Department of Vascular Surgery, KAT General Hospital, Athens, Greece. Electronic address: drkpirg@otenet.gr.
authors.forename: Konstantinos M
authors.initials: KM
authors.lastname: Pirgakis
authors.affiliation: Clinical Biochemistry Department, KAT General Hospital, Athens, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Makris
authors.affiliation: Department of Vascular Surgery, Attikon Hospital, University of Athens, Athens, Greece.
authors.forename: Ilias
authors.initials: I
authors.lastname: Dalainas
authors.affiliation: Vascular Unit, 3rd Surgical Department, Attikon Hospital, University of Athens, Athens, Greece.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Lazaris
authors.affiliation: Department of Vascular Surgery, KAT General Hospital, Athens, Greece.
authors.forename: Chrisostomos K
authors.initials: CK
authors.lastname: Maltezos
authors.affiliation: Department of Vascular Surgery, Attikon Hospital, University of Athens, Athens, Greece.
authors.forename: Christos D
authors.initials: CD
authors.lastname: Liapis
mesh_terms: D058186:Acute Kidney Injury / Q000652:urine*; D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery*; D015415:Biomarkers / Q000652:urine; D015897:Comorbidity; D055316:Cystatin C / Q000652:urine*; D057510:Endovascular Procedures; D005260:Female; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000652:urine*; D011446:Prospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D014656:Vascular Surgical Procedures
chemical_list: D015415:Biomarkers; D055316:Cystatin C