A critical appraisal of the accuracy of the RIFLE and AKIN classifications in defining "acute kidney insufficiency" in critically ill patients.

PURPOSE: The lack of a consensus definition for acute kidney injury (AKI) has led to a great deal of discrepancies and confusion in the literature in this field. Thus, the RIFLE (Risk of renal dysfunction, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-stage renal disease) and Acute Kidney Injury Network (AKIN) classifications were developed by multidisciplinary collaborative groups and were validated by experts in an international consensus conference in 2007 under an umbrella "acute kidney insufficiency" definition.
METHODS: Search in the MEDLINE and PUBMED databases for relevant literature from January 2000 to June 2011 was performed to assess the accuracy of the novel consensus definitions for AKI.
CONCLUSIONS: Both systems are based on serum creatinine level and urine output criteria and are staged in 3 severity levels. A major difference between these 2 classifications is that smaller and more rapid changes in serum creatinine are considered in the AKIN stage 1. Each AKI classification has demonstrated its ability to stratify patients according to their AKI severity and to predict outcomes. No classification system has been shown to be superior over the others. Their application in clinical studies would benefit from standardization and the new Kidney Disease Improving Global Outcomes definition of AKI was recently proposed to achieve this aim. Because these classifications do not allow earlier AKI diagnosis and do not optimize the timing of RRT initiation, they remain of moderate utility from the patient's point of view.