title: Diagnostic performance of fractional excretion of urea in the evaluation of critically ill patients with acute kidney injury: a multicenter cohort study.
abstract: BACKGROUND
  Several factors, including diuretic use and sepsis, interfere with the fractional excretion of sodium, which is used to distinguish transient from persistent acute kidney injury (AKI). These factors do not affect the fractional excretion of urea (FeUrea). However, there are conflicting data on the diagnostic accuracy of FeUrea.
  
  
  METHODS
  We conducted an observational, prospective, multicenter study at three ICUs in university hospitals. Unselected patients, except those with obstructive AKI, were admitted to the participating ICUs during a six-month period. Transient AKI was defined as AKI caused by renal hypoperfusion and reversal within three days. The results are reported as medians (interquartile ranges).
  
  
  RESULTS
  A total of 203 patients were included. According to our definitions, 67 had no AKI, 54 had transient AKI and 82 had persistent AKI. FeUrea was 39% (28 to 40) in the no-AKI group, 41% (29 to 54) in the transient AKI group and 32% (22 to 51) in the persistent AKI group (P = 0.12). FeUrea was of little help in distinguishing transient AKI from persistent AKI, with the area under the receiver operating characteristic curve being 0.59 (95% confidence interval, 0.49 to 0.70; P = 0.06). Sensitivity was 63% and specificity was 54% with a cutoff of 35%. In the subgroup of patients receiving diuretics, the results were similar.
  
  
  CONCLUSIONS
  FeUrea may be of little help in distinguishing transient AKI from persistent AKI in critically ill patients, including those receiving diuretic therapy. Additional studies are needed to evaluate alternative markers or strategies to differentiate transient from persistent AKI.
authors.affiliation: Medical-Surgical Intensive Care Unit, Saint-Etienne University Hospital, and Jean Monnet University, Avenue Albert Raymond, F-42270 Saint-Etienne, France. michael.darmon@chu-st-etienne.fr
authors.forename: Michael
authors.initials: M
authors.lastname: Darmon
authors.forename: Francois
authors.initials: F
authors.lastname: Vincent
authors.forename: Jean
authors.initials: J
authors.lastname: Dellamonica
authors.forename: Frederique
authors.initials: F
authors.lastname: Schortgen
authors.forename: Frederic
authors.initials: F
authors.lastname: Gonzalez
authors.forename: Vincent
authors.initials: V
authors.lastname: Das
authors.forename: Fabrice
authors.initials: F
authors.lastname: Zeni
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
authors.forename: Gilles
authors.initials: G
authors.lastname: Bernardin
authors.forename: Yves
authors.initials: Y
authors.lastname: Cohen
authors.forename: Benoit
authors.initials: B
authors.lastname: Schlemmer
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis* / Q000503:physiopathology / Q000652:urine*; D000368:Aged; D015415:Biomarkers; D015331:Cohort Studies; D016638:Critical Illness; D004232:Diuretics / Q000627:therapeutic use; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018805:Sepsis / Q000503:physiopathology / Q000628:therapy; D014508:Urea / Q000652:urine*
chemical_list: D015415:Biomarkers; D004232:Diuretics; D014508:Urea