Renal/Sepsis
A critical appraisal of the accuracy of the RIFLE and AKIN classifications in defining “acute kidney insufficiency” in critically ill patients

https://doi.org/10.1016/j.jcrc.2012.06.012Get rights and content

Abstract

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.

Introduction

Acute kidney injury (AKI) is a common and serious complication of many critical illnesses. Acute kidney injury consists of a rapid and sustained decline in the glomerular filtration rate (GFR) that results in the inability of the kidneys to eliminate nitrogenous waste products or to maintain proper fluid and electrolyte balances. The proportion of critically ill patients admitted with or who develop AKI during their intensive care unit (ICU) stay ranged from 5% to 60% in the literature according to the definition used and the case mix of the patient population studied. Among AKI sufferers, 5% to 30% require the use of renal replacement therapy (RRT) [1], [2]. Although many advances have been made in understanding its pathophysiology and in the development of RRT in the intensive care setting, AKI still carries a significant morbidity and a 20% to 80% mortality rate [3], [4].

One of the most significant problems has been for a long time the absence of a consensus on the definition of AKI. The existence of more than 35 definitions for AKI accounts for the wide disparity and inconsistency of the literature. Consequently, several classifications of AKI have been developed during the last decade to better characterize this disease, to assess the severity of organ dysfunction and prognosis, and to harmonize the literature.

In 2004, the “Acute Dialysis Quality Initiative” (ADQI ) group proposed a definition of AKI named RIFLE (Risk of renal dysfunction, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-stage renal disease) that was based on separate criteria including GFR, creatinine, and urinary output (Fig. 1) [5]. It includes 3 levels of increasing severity of renal dysfunction (RIFLE-R for Risk, RIFLE-I for Injury, and RIFLE-F for Failure of renal function) and 2 levels of clinical outcomes (RIFLE-L for Loss of renal function and RIFLE-E for End-stage kidney disease). The major strength of this classification system is that it considers the change of any measure of renal function from baseline. In a patient without known chronic renal insufficiency and in whom the baseline value of creatinine is unknown, the modification of diet in renal disease (MDRD) formula with a creatinine clearance of 75 mL/min per 1.73 m2 provides an estimate of a baseline creatinine concentration (see Table 1) [6].

Concurrently, an independent collaborative network named Acute Kidney Injury Network (AKIN) composed of experts in the field of acute renal failure (ARF) selected from participating nephrology and critical care societies proposed the term AKI to reflect the entire spectrum of ARF [7]. A second interim definition and staging system for AKI were proposed in the first AKIN conference held in Amsterdam in September 2005 [7]. This new definition took into account minor serum creatinine concentration variations (Fig. 1). The staging system includes 3 levels of severity, with stages 2 and 3 corresponding to the items “injury to the kidney” and “failure of kidney function” of the RIFLE classification. This definition introduced a temporal dimension into the definition of AKI. The 48-hour period eliminated progressive and modest changes in creatinine levels that cannot be classified as acute and for which an impact on morbid-mortality was not demonstrated. Finally, patients who receive RRT were classified in the highest level of the staging system, regardless of their serum creatinine concentration or urine output at the time of commencement of RRT.

Based on the abundant literature in the field of AKI, a consensus for AKI definition was achieved by a panel of experts during an international consensus conference in 2007, and their official statement titled “Prevention and Management of ARF in the ICU patient” was recently published [8]. Briefly, the jury recommended the use of the phrase “acute kidney insufficiency” to refer to relative inadequacy of renal function and suggested that AKI definitions should be based on the criteria of the AKIN or RIFLE classifications to integrate both urine output and creatinine measurements.

The following review describes the evidence about the diagnostic validity and prognostic capacities of the RIFLE and AKIN classifications in critically ill patients and discusses their clinical application, potential interest, and limitations in the ICU setting.

This review of literature focusing on AKI definition is, however, not exhaustive and diagnostic, or prognostic accuracy of the Bellomo score [9]; the Sequential Organ Failure Assessment (SOFA) renal subscore [10], [11]; some specific prognostic scores of patients with AKI, such as the SHARF score (“Stuivenberg Hospital Acute Renal Failure”) [12], [13]; or other old scores [14], [15], [16] are not discussed.

Section snippets

Materials and methods

We did a critical appraisal of RIFLE and AKIN classification by performing a literature search from January 2000 to June 2011 to find publications on AKI definition in critically ill patients. The review was performed using MEDLINE and PUBMED electronic databases with the following key words: acute renal failure, acute renal insufficiency, acute kidney injury and acute kidney insufficiency, RIFLE and AKIN classifications, outcome, prognosis, intensive care, death, and mortality. All articles

The RIFLE classification

Many studies assessed the incidence of AKI according to the RIFLE classification and evaluated their related prognosis according to the rates of need for RRT, recovery from AKI, and mortality (Table 2, Table 3). Despite great variations of the morbidity and mortality rates resulting in a great heterogeneity in the case-mix populations, the study design, the length of follow-up, and/or the criteria used for the AKI definition according to the RIFLE classification, in all studies [17], [18], [19]

Discussion

This review of the relevant and recent literature does not demonstrate clear superiority of either the AKIN or the RIFLE classifications on the other one regarding their sensitivity and specificity for AKI diagnosis. The apparent incidence of AKI is quite similar when using either of the 2 definitions (Table 2, Table 4). As compared with RIFLE, the smaller change in serum creatinine concentration used to define AKI in the AKIN classification generates a greater number of patients classified in

Conclusion

The RIFLE and AKIN classifications have led to a consensus definition of AKI in the intensive care setting. Both definitions have demonstrated their clinical relevance, including a good correlation between the degree of AKI severity and outcomes. However, both definitions of AKI remain far from perfect. Regarding the use and application of these staging systems, evidence for a wide heterogeneity still emerges from a review of the recent literature. This heterogeneity may explain, at least in

References (68)

  • P.G. Metnitz et al.

    Effect of acute renal failure requiring renal replacement therapy on outcome in critically ill patients

    Crit Care Med

    (2002)
  • R. Thadhani et al.

    Acute renal failure

    N Engl J Med

    (1996)
  • R. Bellomo et al.

    Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

    Crit Care

    (2004)
  • A.S. Levey et al.

    A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group

    Ann Intern Med

    (1999)
  • R.L. Mehta et al.

    Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury

    Crit Care

    (2007)
  • L. Brochard et al.

    An Official ATS/ERS/ESICM/SCCM/SRLF Statement: prevention and management of acute renal failure in the ICU patient: an international consensus conference in intensive care medicine

    Am J Respir Crit Care Med

    (2010)
  • R. Bellomo et al.

    Acute renal failure: time for consensus

    Intensive Care Med

    (2001)
  • A. de Mendonca et al.

    Acute renal failure in the ICU: risk factors and outcome evaluated by the SOFA score

    Intensive Care Med

    (2000)
  • R. Moreno et al.

    The use of maximum SOFA score to quantify organ dysfunction/failure in intensive care. Results of a prospective, multicentre study. Working Group on Sepsis related Problems of the ESICM

    Intensive Care Med

    (1999)
  • R.L. Lins et al.

    Prognostic value of a new scoring system for hospital mortality in acute renal failure

    Clin Nephrol

    (2000)
  • R.L. Lins et al.

    Re-evaluation and modification of the Stuivenberg Hospital Acute Renal Failure (SHARF) scoring system for the prognosis of acute renal failure: an independent multicentre, prospective study

    Nephrol Dial Transplant

    (2004)
  • R.L. Mehta et al.

    Refining predictive models in critically ill patients with acute renal failure

    J Am Soc Nephrol

    (2002)
  • G.M. Chertow et al.

    Predictors of mortality and the provision of dialysis in patients with acute tubular necrosis. The Auriculin Anaritide Acute Renal Failure Study Group

    J Am Soc Nephrol

    (1998)
  • F. Liano et al.

    Prognosis of acute tubular necrosis: an extended prospectively contrasted study

    Nephron

    (1993)
  • T. Ali et al.

    Incidence and outcomes in acute kidney injury: a comprehensive population-based study

    J Am Soc Nephrol

    (2007)
  • S.M. Bagshaw et al.

    A comparison of the RIFLE and AKIN criteria for acute kidney injury in critically ill patients

    Nephrol Dial Transplant

    (2008)
  • M. Bell et al.

    Optimal follow-up time after continuous renal replacement therapy in actual renal failure patients stratified with the RIFLE criteria

    Nephrol Dial Transplant

    (2005)
  • A. Bihorac et al.

    Incidence, clinical predictors, genomics, and outcome of acute kidney injury among trauma patients

    Ann Surg

    (2010)
  • R. Cartin-Ceba et al.

    Evaluation of “Loss” and “End stage renal disease” after acute kidney injury defined by the Risk, Injury, Failure, Loss and ESRD classification in critically ill patients

    Intensive Care Med

    (2009)
  • C.H. Chang et al.

    Acute kidney injury classification: comparison of AKIN and RIFLE criteria

    Shock

    (2010)
  • J. Chen et al.

    Postliver transplant acute renal injury and failure by the RIFLE criteria in patients with normal pretransplant serum creatinine concentrations: a matched study

    Transplantation

    (2011)
  • E. Cholongitas et al.

    RIFLE classification as predictive factor of mortality in patients with cirrhosis admitted to intensive care unit

    J Gastroenterol Hepatol

    (2009)
  • D.N. Cruz et al.

    North East Italian Prospective Hospital Renal Outcome Survey on Acute Kidney Injury (NEiPHROS-AKI): targeting the problem with the RIFLE criteria

    Clin J Am Soc Nephrol

    (2007)
  • D. du Cheyron et al.

    The attributable mortality of acute renal failure in critically ill patients with liver cirrhosis

    Intensive Care Med

    (2005)
  • Cited by (28)

    • Risk factors for in-hospital mortality and acute kidney injury in neonatal-pediatric patients receiving extracorporeal membrane oxygenation

      2021, Journal of the Formosan Medical Association
      Citation Excerpt :

      The RIFLE classification (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) was first proposed by the Acute Dialysis Quality Initiative group to standardize the study of AKI. Subsequently, the AKI Network (AKIN) classification was modified; according to this classification, AKI is defined as an increase of ≥0.3 mg/dL in the serum creatinine (Scr) level in a 48-h period.5 The most recent Kidney Disease Improving Global Outcome (KDIGO) consensus definition utilizes a staged severity classification referenced to a change from the baseline function to the need for renal support therapy (RST) to characterize the severity of AKI.4,6,7

    • How do i rapidly and correctly identify acute kidney injury?

      2019, Evidence-Based Practice of Critical Care
    • Effects of differential-phase remote ischemic preconditioning intervention in laparoscopic partial nephrectomy: A single blinded, randomized controlled trial in a parallel group design

      2017, Journal of Clinical Anesthesia
      Citation Excerpt :

      However, it has been shown that prolonged warm ischemia time results in renal function deficiency [16]. Traditionally the diagnosis of AKI has relied on the basis of changes in blood creatinine or urine output [17,18]. In the past decade, various serum and urinary biomarkers has been used to evaulate AKI, the most valuable of which are NGAL, IL-18, CysC, and KIM-1 [19].

    • Comparison of the RIFLE, AKIN, and KDIGO Diagnostic Classifications for Acute Renal Injury in Patients Undergoing Liver Transplantation

      2016, Transplantation Proceedings
      Citation Excerpt :

      Administering FFP adversely affects LT recipients [21], for example, by increasing the incidence of ARI and nosocomial infections [23], as well as mortality rates. Mortality rates are expected to increase as ARI progresses from initial to subsequent stages, according to the RIFLE and AKIN classifications [24]. In this study, ARI severity and increased mortality rate were significantly related during the first 28 days after surgery (P = .002, P = .0001, and P = .0001 by RIFLE, AKIN, and KDIGO, respectively).

    • Clinical outcome of kidney transplantation from deceased donors with acute kidney injury by Acute Kidney Injury Network criteria

      2014, Journal of Critical Care
      Citation Excerpt :

      However, owing to several limitations, a modification of the RIFLE criteria, known as the Acute Kidney Injury Network (AKIN) classification system, was proposed [7,8]. These criteria have now been evaluated in a number of clinical studies of patients with AKI outside the kidney transplantation (KT) setting and have shown reliable predictability for renal outcome and patient mortality [3,6,9]. However, the previously reported standardized criteria of AKI for nontransplanted kidneys have rarely been used for potential kidney donors for the prediction of renal allograft outcome; another AKI criteria, the AKIN criteria, have not been adopted in this field [3].

    View all citing articles on Scopus
    View full text