The Prognostic Role of RDW in Hospitalized Heart Failure Patients with and Without Chronic Kidney Disease

Background: Chronic kidney disease (CKD) and heart failure (HF) are interrelated conditions that exacerbate each other through mechanisms like fluid retention, neurohormonal activation, and inflammation. Red blood cell distribution width (RDW), a measure of red blood cell size variability, has emerged as a potential prognostic marker in HF. This study aimed to assess the prognostic value of RDW in HF patients, both with and without CKD, focusing on all-cause mortality and HF rehospitalizations. Methods: This observational retrospective study included 171 patients hospitalized for acute decompensated HF in a tertiary university hospital in Greece. Patients were divided into two groups based on their estimated glomerular filtration rate (eGFR), as Group 1 (eGFR < 60 mL/min/1.73 m2) and Group 2 (eGFR ≥ 60 mL/min/1.73 m2). RDW was measured upon admission, and outcomes of interest were all-cause mortality and HF rehospitalizations over a median follow-up period of 6.1 months. Statistical analyses included Kaplan–Meier survival curves, whereas the discrimination traits of RDW were evaluated by constructing receiver operating characteristic (ROC) curves and by calculating the area under the ROC curve (AUC). A p-value <0.05 was indicative of a statistically important result. Results: Patients in Group 1 (eGFR < 60 mL/min/1.73 m2) were older (80 (73–86) vs. 75 (62–83)) and manifested higher median RDW values (16.6 (15.0–18.8) vs. 15.6 (14.1–17.8)) and received less frequent (57.9% vs. 75%) mineralocorticoid receptor antagonists (MRAs) as compared to those in Group 2 (eGFR ≥ 60 mL/min/1.73 m2). RDW demonstrated better prognostic value in predicting combined mortality and rehospitalization outcomes in Group 2 patients (area under the curve: 0.70; 95% CI (0.62–0.80)) compared to those in Group 1 (area under the curve: 0.53; 95% CI (0.35–0.72)). No statistically significant differences (p = 0.579) were observed in survival between patients with high (≥15%) and low (<15%) RDW values in the overall population, though trends favored worse outcomes with elevated RDW. Similarly, no significant differences (p = 0.374) were observed in survival between patients with high (Group 2) and low (Group 1) eGFR values. Conclusions: RDW appears to be a meaningful prognostic biomarker for HF patients, particularly in those without CKD. Further multicenter studies are needed to validate its clinical utility and potential for guiding treatment in this high-risk population.