Research

Acute kidney injury in intensive care unit patients: a comparison between the RIFLE and the Acute Kidney Injury Network classifications

José António Lopes¹ , Paulo Fernandes¹ , Sofia Jorge¹ , Sara Gonçalves¹ , António Alvarez² , Zélia Costa e Silva² , Carlos França² and Mateus Martins Prata¹

¹Department of Nephrology and Renal Transplantation, Hospital de Santa Maria, Av. Prof. Egas Moniz, Lisboa 1649-035, Portugal

²Department of Intensive Medicine, Hospital de Santa Maria, Av. Prof. Egas Moniz, Lisboa 1649-035, Portugal

author email corresponding author email

Critical Care 2008, 12:R110doi:10.1186/cc6997

Published:	28 August 2008

Abstract

Introduction

Whether discernible advantages in terms of sensitivity and specificity exist with Acute Kidney Injury Network (AKIN) criteria versus Risk, Injury, Failure, Loss of Kidney Function, End-stage Kidney Disease (RIFLE) criteria is currently unknown. We evaluated the incidence of acute kidney injury and compared the ability of the maximum RIFLE and of the maximum AKIN within intensive care unit hospitalization in predicting inhospital mortality of critically ill patients.

Methods

Patients admitted to the Department of Intensive Medicine of our hospital between January 2003 and December 2006 were retrospectively evaluated. Chronic kidney disease patients undergoing dialysis or renal transplant patients were excluded from the analysis.

Results

In total, 662 patients (mean age, 58.6 ± 19.2 years; 392 males) were evaluated. AKIN criteria allowed the identification of more patients as having acute kidney injury (50.4% versus 43.8%, P = 0.018) and classified more patients with Stage 1 (risk in RIFLE) (21.1% versus 14.7%, P = 0.003), but no differences were observed for Stage 2 (injury in RIFLE) (10.1% versus 11%, P = 0.655) and for Stage 3 (failure in RIFLE) (19.2% versus 18.1%, P = 0.672). Mortality was significantly higher for acute kidney injury defined by any of the RIFLE criteria (41.3% versus 11%, P < 0.0001; odds ratio = 2.78, 95% confidence interval = 1.74 to 4.45, P < 0.0001) or of the AKIN criteria (39.8% versus 8.5%, P < 0.0001; odds ratio = 3.59, 95% confidence interval = 2.14 to 6.01, P < 0.0001). The area under the receiver operator characteristic curve for inhospital mortality was 0.733 for RIFLE criteria (P < 0.0001) and was 0.750 for AKIN criteria (P < 0.0001). There were no statistical differences in mortality by the acute kidney injury definition/classification criteria (P = 0.72).

Conclusions

Although AKIN criteria could improve the sensitivity of the acute kidney injury diagnosis, it does not seem to improve on the ability of the RIFLE criteria in predicting inhospital mortality of critically ill patients.