Intensive Care Medicine

, Volume 35, Issue 10, pp 1692–1702 | Cite as

Acute kidney injury in critically ill patients classified by AKIN versus RIFLE using the SAPS 3 database

  • Michael JoannidisEmail author
  • Barbara Metnitz
  • Peter Bauer
  • Nicola Schusterschitz
  • Rui Moreno
  • Wilfred Druml
  • Philipp G. H. Metnitz



Acute kidney injury (AKI) is associated with significantly increased morbidity and mortality. To provide a uniformly accepted definition, the RIFLE classification was introduced by the Acute Dialysis Quality Initiative, recently modified by the Acute Kidney Injury Network (AKIN), suggesting staging of AKI based on dynamic changes within 48 h. This study compares these two classification systems with regard to outcome.


Cohort analysis of SAPS 3 database.


Sixteen thousand seven hundred and eighty-four ICU patients from 303 ICUs were analysed. Classification was performed according to RIFLE (Risk, Injury, Failure) or according to AKIN (stage 1, 2, 3) without including a requirement of renal replacement therapy in the analysis. Changes of serum creatinine as well as urinary output were assessed for both AKIN and RIFLE during the first 48 h of ICU admission. Primary endpoint was hospital mortality.


Incidence of AKI in our population of critically ill patients was found to range between 28.5 and 35.5% when applying AKIN and RIFLE criteria, respectively, associated with increased hospital mortality averaging 36.4%. Observed-to-expected mortality ratios revealed excess mortality conferred by any degree of AKI increasing from 0.81 for patients classified as non-AKI up to 1.31 and 1.23 with AKIN stage 3 or RIFLE Failure, respectively. AKIN misclassified 1,504 patients as non-AKI compared to RIFLE which misclassified 504 patients.


Acute kidney injury classified by either RIFLE or AKIN is associated with increased hospital mortality. Despite presumed increased sensitivity by the AKIN classification, RIFLE shows better robustness and a higher detection rate of AKI during the first 48 h of ICU admission.


Acute kidney injury Epidemiology Incidence Outcome Urinary output Creatinine 



This work was supported by the Oesterrreichische Nationalbank Jubilaeumsfondsprojekt Nr. 12690 (P. M.) and Nr. 12094 (M. J.).

Conflict of interest statement


Supplementary material

134_2009_1530_MOESM1_ESM.doc (354 kb)
Electronic supplementary material (DOC 354 kb)


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Michael Joannidis
    • 1
    Email author
  • Barbara Metnitz
    • 2
  • Peter Bauer
    • 2
  • Nicola Schusterschitz
    • 1
  • Rui Moreno
    • 4
  • Wilfred Druml
    • 3
  • Philipp G. H. Metnitz
    • 5
  1. 1.Intensive Care Unit, Department of Internal Medicine IMedical University InnsbruckInnsbruckAustria
  2. 2.Department of Medical StatisticsMedical UniversityViennaAustria
  3. 3.Department of Internal Medicine IIIUniversity HospitalViennaAustria
  4. 4.Unidade de Cuidados Intensivos PolivalenteHospital de St. António dos Capuchos, Centro Hospitalar de Lisboa Central E.P.ELisbonPortugal
  5. 5.Department of Anesthesia and General Intensive Care MedicineMedical UniversityViennaAustria

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