Abstract
The red blood cell distribution width (RDW) to albumin ratio (RAR), a novel indicator of inflammation, is known to be associated with a poor prognosis in various diseases. The purpose of this study was to investigate whether RAR is also associated with mortality in critically ill patients with acute kidney injury (AKI). A retrospective observational study was conducted using the Medical Information Mart for Intensive Care III (MIMIC-III) database, which contains comprehensive clinical data relating to patients with AKI between 2001 and 2012. Patients were grouped into quartiles (Q1–Q4) according to the RAR. All-cause mortality was then compared across the four groups using Kaplan-Meier analysis. Cox proportional hazard models and subgroup analyses were use to investigate RAR and the prognosis of patients with AKI. A total of 3826 critically ill patients with AKI were included in this study. Based on Kaplan-Meier curve analysis, the patient group with a high-RAR exhibited elevated rates of mortality at 28 days (log-rank p < 0.001). Multivariable Cox proportional hazard models identified RAR as a significant predictor of mortality at 28 days (Hazard ratio, HR (95% Confidence Interval, CI) 1.07 (1.03–1.11), p < 0.001), in the hospital (HR (95% CI) 1.08 (1.05–1.12), p < 0.001), and in the intensive care unit (ICU) (HR (95% CI) 1.06 (1.02–1.11), p = 0.004). Furthermore, the subgroup analysis showed that the effect of the RAR was significantly greater in patients with diabetes than in those without diabetes (p for interaction = 0.005). As the RAR increased, the mortality rate within 28 days of hospitalization and in the ICU also increased. Thus, the RAR has the potential to become an important and practical indicator for identifying a poor prognosis in critically ill patients with AKI.