Comparison of RIFLE with and without urine output criteria for acute kidney injury in critically ill patients: a task still not concluded!

Abstract

In a recent issue of Critical Care, we read with interest the article by Wlodzimirow and colleagues [1], who prospectively studied the Risk Injury Failure Loss Endstage renal disease (RIFLE) [2] classifi cation with serum creatinine (SCr) and urine output (UO) (RIFLE SCr+UO ) and without UO criteria (RIFLE SCr ) for acute kidney injury (AKI) in 260 critically ill patients. RIFLE SCr signifi cantly underestimated the presence of AKI on admission and during the fi rst week in the intensive care unit and signifi cantly delayed AKI diagnosis. Th ose are important fi ndings that corroborate the utility of simultaneously using both criteria as proposed by the Acute Dialysis Quality Initiative workgroup [2]. Th e authors also found that RIFLE SCr was associated with higher mortality than RIFLE SCr+UO . Th is observation should be interpreted with extreme caution, as this association has not been tested by multivariate analysis. Data regarding the impact on mortality of RIFLE defi ned by SCr and UO or by SCr are not conclusive. For example, in a systematic review, the relative risk for death among studies that used RIFLE SCr+UO was lower than in those using RIFLE SCr [3]. Previously, however, we did not fi nd any diff erence in terms of mortality for RIFLE SCr+UO (Risk, odds ratio (OR) 2.69; Injury, OR 2.01; Failure, OR 3.59; AKI of any category, 2.78; area under the receiver operator characteristic (AUROC), 0.733) or for RIFLE SCr (Risk, OR 2.63; Injury, OR 2.12; Failure, OR 3.2; AKI of any category, 2.68; AUROC, 0.729) [4]. Th erefore, prospective studies with a large number of patients are still needed to better determine the impact on mortality of RIFLE defi ned by SCr+UO criteria or by SCr criteria.