Comparison of absolute serum creatinine changes versus Kidney Disease: Improving Global Outcomes consensus definitions for characterizing stages of acute kidney injury

...irrespective of the definition of AKI, and validation of the presence of AKI and its severity, we need to apply these definitions in a systematic way to both research and clinical care to determine the ultimate utility of them...The Kidney Disease: Improving Global Outcomes (KDIGO) system for classification of acute kidney injury (AKI) severity utilizes a staging schema based on relative changes in serum creatinine (sCr) concentration and urine output. This study compares the in-hospital mortality associated with KDIGO-defined AKI stages and AKI stages defined by absolute sCr increases (Delta-Creatinine). The study included an analysis of hospital discharge and laboratory data from an urban academic medical center over a 1-year period. Including adult in-patients undergoing two or more sCr measurements, the study classified AKI stages using the KDIGO consensus standards as well as absolute increases in sCr (Delta-Creatinine); Stage 0, sCr increase 0.3 mg/dL, Stage 1, sCr increase 0.30.69 mg/dL, Stage 2, sCr increase 0.71.19 mg/dL and Stage 3, sCr increase 1.2 mg/dL or initiation of renal replacement therapy. The Delta-Creatinine cut-points were defined to optimize discrimination of in-patient mortality between AKI stages. The associations between KDIGO and Delta-Creatinine AKI stages and in-hospital mortality were compared using the time-dependent hazard ratios (HRs) and the net reclassification improvement (NRI). Of the 19 878 hospitalizations included in the analysis, the prevalence of AKI was 23.4 as defined by the KDIGO criteria. The Delta-Creatinine system discriminated the differences between adjacent AKI stages (i.e. 1 versus 0, 2 versus 1, 3 versus 3) earlier than the KDIGO system. The NRI between Delta-Creatinine and KDIGO for the prediction of mortality was 9.7 [95 confidence interval (CI) 6.213.2]. Stratification by age, sex, race and history of chronic kidney disease (CKD) resulted in similar NRI values. The Delta-Creatinine system, based on the absolute increases in sCr, provides a promising alternative to the KDIGO system for characterizing the severity of AKI and its associations with in-patient mortality.