Red cell distribution width-to-albumin ratio and chronic kidney disease mortality in adults: A population-based...

Chronic kidney disease (CKD) is associated with systemic inflammation and malnutrition, but prognostic tools integrating these pathways are lacking. This study investigated the red cell distribution width-to-albumin ratio (RAR) as a novel biomarker for predicting all-cause mortality in CKD patients. We conducted a retrospective cohort study using National Health and Nutrition Examination Survey 1999 to 2020 data (N = 40,133, including 6795 CKD cases). The RAR was derived from standardized laboratory measurements. Multivariable Cox regression with restricted cubic splines analyzed mortality risk, complemented by time-dependent receiver operating characteristic analysis and mediation analysis. Models were adjusted for 38 covariates spanning demographics, comorbidities, and biochemical parameters. Among 40,133 participants (6795 CKD cases) from the National Health and Nutrition Examination Survey (1999-2020), elevated RAR was independently linked to higher mortality risk (adjusted hazard ratio [HR] = 2.12, 95% confidence interval [CI] = 1.66-2.70, P < .001). Restricted cubic spline analysis revealed a nonlinear association, with an optimal RAR threshold of 4.26. Patients with RAR > 4.26 faced a 70% increased mortality risk compared to those ≤4.26 (HR = 1.70, 95% CI = 1.58-1.82, P < .001). RAR surpassed red cell distribution width alone in predicting 1-year mortality (area under the curve = 0.59, 95% CI = 0.57-0.60 vs 0.55, 95% CI = 0.54-0.57; P < .001). Subgroup analyses showed stronger mortality associations in males (HR = 2.39, 95% CI = 1.96-2.69), alcohol consumers (HR = 2.60, 95% CI = 2.20-3.01), and nonanemic individuals (HR = 2.45, 95% CI = 2.10-2.85; P interaction < .05). The neutrophil-to-lymphocyte ratio mediated 7.89% of RAR's mortality risk. RAR, a composite biomarker reflecting erythrocyte instability and inflammation, provides robust prognostic value for CKD mortality. Its threshold (4.26) enables practical risk stratification, particularly in resource-limited settings. These findings support RAR's integration into clinical workflows to improve personalized CKD management.