A comparison of four methods to define timing of acute kidney injury

RIFLE provides standardized criteria for defining acute kidney injury (AKI) [ 1 ]. It is based on changes in serum creatinine (sCr), in relation to a premorbid sCr, and on urine output. When premorbid sCr is unknown, baseline sCr is estimated. Often only sCr is used (RIFLEcreat). Thus there are four methods for defining AKI: actual RIFLE, actual RIFLEcreat, estimated RIFLE and estimated RIFLEcreat. There is much interest for biomarkers predicting early AKI [ 2 ]. Critical for determining a biomarker's performance of AKI is the diagnosis of the first day of AKI (AKI-0). We compared the impact of four AKI definitions on determining AKI-0.