Use of the Renal Angina Index in Determining Acute Kidney Injury

Introduction: The renal angina index (RAI) is determined based on changes in the creatinine and condition scores of patients. The aim of this study is to evaluate the efficacy of the RAI in predicting persistent acute kidney injury (AKI) in Asian intensive care unit (ICU) patients. Methods: This is a subanalysis of 3 prospective studies conducted in Japan and Thailand. The RAI was calculated for all enrolled patients using the method of Goldstein and colleagues, with a minor modification for adults on day 2. To determine the accuracy of RAI further, we evaluated a subgroup of patients for whom baseline serum creatinine values were available at ICU admission (i.e., those with hospital acquired AKI). AKI biomarkers were evaluated for their efficacy in improving the performance of RAI. The outcome was defined as AKI stage 2 or 3 over 48 hours. Results: Of the 263 patients analyzed, a total of 22 progressed to stage 2 or 3 AKI over 48 hours. The RAI was associated with an area under the curve (AUC) of 0.63 in receiver-operating characteristics analysis, with a cutoff of 10. In those admitted from general wards, the RAI had good performance, with an AUC of 0.73 and a cutoff of 6. A combination of L-type fatty acid-binding protein with the RAI improved the predictive performance for assessing persistent AKI with an AUC of 0.79. Conclusion: The RAI may be effective in predicting persistent AKI in adult patients admitted from general wards. Incorporation of AKI biomarkers into the RAI may potentially improve prediction.