Outcome definitions in non-dialysis intervention and prevention trials in acute kidney injury (AKI)

Nephrol Dial Transplant. 2010 Jan;25(1):107-18. doi: 10.1093/ndt/gfp501. Epub 2009 Oct 7.


Background: The risk, injury, failure, loss-of-function, end-stage-renal-failure (RIFLE) and acute kidney injury network (AKIN) consensus definitions of acute kidney injury (AKI) were established in part to facilitate comparison of trials. Contrast-induced nephropathy (CIN) has traditionally used a less demanding definition.

Objectives: To review use of RIFLE and AKIN as AKI trial outcome variables and contrast these with outcomes for CIN.

Methods: We conducted a search of PubMed from 1 January 2005 to 31 December 2008 and 9 trial registries for randomized control trials for preventional or interventional treatment of AKI and CIN.

Results: RIFLE or AKIN were outcome variables in 36% (n = 8) of the published (n = 22) and 18% (n = 4) of the current (n = 22) AKI trials. RIFLE was used to triage to intervention in three trials. The urine output definition of RIFLE and AKIN was an outcome in only two trials. In 18% (n = 8) of AKI trials, the CIN definition (increase in serum creatinine of > or =25% and/or > or =44 micromol/l) was the primary outcome. This was also the primary outcome in 56% (n = 13) of published (n = 12) and current (n = 11) CIN trials. Three published CIN trials used RIFLE or AKIN as an outcome (13%). The duration over which outcomes were determined varied from 24 h to 7 days.

Conclusions: Considerable heterogeneity remains in outcome variables of AKI and CIN clinical trials. Even when the RIFLE or AKIN criteria were used, they were not applied consistently. There is a need for further consensus on surrogate outcome variables.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Kidney Injury / diagnosis*
  • Acute Kidney Injury / physiopathology*
  • Acute Kidney Injury / urine
  • Biomarkers / metabolism
  • Contrast Media / adverse effects
  • Creatinine / blood
  • Humans
  • Kidney Diseases / chemically induced
  • Kidney Diseases / diagnosis*
  • Kidney Diseases / physiopathology*
  • Outcome Assessment, Health Care*
  • Prognosis
  • Randomized Controlled Trials as Topic
  • Retrospective Studies
  • Severity of Illness Index


  • Biomarkers
  • Contrast Media
  • Creatinine