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

<b>Background:</b> 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. <b>Methods:</b> 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 <i>p</i>-value <0.05 was indicative of a statistically important result. <b>Results:</b> 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 (<i>p</i> = 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 (<i>p</i> = 0.374) were observed in survival between patients with high (Group 2) and low (Group 1) eGFR values. <b>Conclusions:</b> 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.