Red Cell Distribution Width (Rdw) As A Marker Of Anemia Severity And Inflammation In Chronic Kidney Disease: A Cross-Sectional Analysis

Background: Red cell distribution width (RDW) is an automated complete blood count index reflecting anisocytosis. Beyond classical hematologic interpretation, RDW has been linked to inflammation and adverse outcomes in chronic kidney disease (CKD), but its utility as a pragmatic marker of anemia severity and inflammatory burden requires confirmation within routine-care cohorts (Salvagno et al., 2015; Deng et al., 2022). Methods: We performed a hospital-based cross-sectional study of adults with CKD managed in a tertiary nephrology service between January 2022 and December 2024. CKD was staged using eGFR estimated by the CKD-EPI 2021 creatinine equation (Inker et al., 2021) and categorized according to KDIGO guidance (KDIGO CKD Work Group, 2024). RDW was analyzed as a continuous exposure and by quartiles. Outcomes included hemoglobin (Hb), anemia and severe anemia, and inflammation measured by C-reactive protein (CRP). Multivariable linear and logistic regression adjusted for age, sex, eGFR, diabetes, CRP and albumin. Results: The cohort included 412 patients (mean age 64.8 ± 13.1 years; 57.8% male); 352 (85.4%) were non-dialysis CKD and 60 (14.6%) were dialysis-treated. Mean eGFR was 34.6 ± 18.9 ml/min/1.73 m², Hb 11.2 ± 1.9 g/dL, RDW 14.6 ± 1.8%, and median CRP 6.4 mg/L (IQR 2.1–14.8). RDW increased across CKD stages and correlated inversely with eGFR (r = −0.41, p < 0.001). Hb declined across RDW quartiles (12.6 ± 1.4 to 9.8 ± 1.8 g/dL; p-trend < 0.001), while CRP increased (2.8 to 13.6 mg/L across quartiles; r = 0.38, p < 0.001). In adjusted models, each +1% RDW was associated with lower Hb (β = −0.42 g/dL, 95% CI −0.49 to −0.34; p < 0.001) and higher log(CRP) (β = 0.27, 95% CI 0.18–0.36; p < 0.001); RDW Q4 vs Q1 predicted severe anemia (OR = 3.9, 95% CI 2.3–6.6; p < 0.001). Conclusion: RDW is independently associated with anemia severity and inflammatory burden across CKD stages, supporting its use as a low-cost contextual marker to augment routine CKD anemia assessment (Babitt et al., 2026; KDIGO CKD Work Group, 2024).