Prognostic value of red blood cell distribution width and lactate for short- and long-term mortality in critically ill patients with acute kidney injury

Introduction: Acute kidney injury in intensive care units is associated with high mortality, highlighting the need for simple biomarkers to improve prognostic stratification. Objective: To evaluate the prognostic value of RDW and lactate for short- and long-term mortality in critically ill patients with acute kidney injury. Materials and methods: An analytical study using an open dataset including 2,139 patients with acute kidney injury during their first ICU admission. The main biomarkers were RDW and lactate measured within the first 24 hours, classified into four combined categories. Outcomes were 28-day, 90-day, and 1-year mortality. Multivariable logistic regression, Kaplan–Meier survival curves, and adjusted Cox proportional hazards models were used. Results were reported as odds ratios (OR) and hazard ratios (HR) with 95% confidence intervals. Results: Mortality increased across the combined RDW–lactate categories, with the highest rates observed in patients with both biomarkers elevated: 32.1% at 28 days, 43.6% at 90 days, and 53.0% at 1 year. In adjusted models, both RDW and lactate were independently associated with higher mortality. The RDW × lactate interaction was significant for 90-day mortality (OR 1.13). Cox analysis confirmed a higher risk of 90-day mortality in patients with both biomarkers elevated (HR 1.57). Kaplan–Meier curves showed significant differences in survival (log-rank p< 0.001). Conclusions: The combined evaluation of RDW and lactate may improve short- and long-term mortality risk stratification in critically ill patients with acute kidney injury.