The severity of acute kidney injury predicts progression to chronic kidney disease

Abstract

Acute kidney injury (AKI) is associated with progression to advanced chronic kidney disease (CKD). We tested whether patients who survive AKI and are at higher risk for CKD progression can be identified during their hospital admission, thus providing opportunities to intervene. This was assessed in patients in the Department of Veterans Affairs Healthcare System hospitalized with a primary diagnosis indicating AKI (ICD9 codes 584.xx). In the exploratory phase, three multivariate prediction models for progression to stage 4 CKD were developed. In the confirmatory phase, the models were validated in 11,589 patients admitted for myocardial infarction or pneumonia during the same time frame that had RIFLE codes R, I, or F and complete data for all predictor variables. Of the 5351 patients in the AKI group, 728 entered stage 4 CKD after hospitalization. Models 1, 2, and 3 were all significant with 'c' statistics of 0.82, 0.81, and 0.77, respectively. In model validation, all three were highly significant when tested in the confirmatory patients, with moderate to large effect sizes and good predictive accuracy ('c' 0.81-0.82). Patients with AKI who required dialysis and then recovered were at especially high risk for progression to CKD. Hence, the severity of AKI is a robust predictor of progression to CKD.

Figure 1

Receiver operating characteristic (ROC) curves for models 1–3 in acute kidney injury (AKI) population. (a) ROC curve for model 1 in AKI subjects, c=0.82. (b) ROC curve for model 2 in AKI subjects, c=0.81. (c) ROC curve for model 3 in AKI subjects, c=0.77. Dotted line shows minimum Euclidean distance from ROC curve to the point of optimum sensitivity and specificity.

Figure 2

ROC curves for models 1–3 in CON population. (a) ROC curve for model 1 in CON subjects, c=0.81. (b) ROC curve for model 2 in CON subjects, c=0.81. (c) ROC curve for model 3 in CON subjects, c=0.82.

Figure 3

Acute kidney injury (AKI) patients who survived >1 year. (a) Mean eGFR over time (tertiles). (b) AKI patients who survived >1 year. Mean serum creatinine over time (tertiles). Tertiles were defined based on scores at 1-5 years post-admission. Error bars show the 95% confidence interval at each time point.