Abstract
OBJECTIVES: To investigate the association between red cell distribution width (RDW) and early kidney injury. METHODS: Data were obtained from the 2003-2004 National Health and Nutrition Examination Survey, including 3,633 adult participants. Early kidney injury was defined according to the 2024 Kidney Disease: Improving Global Outcomes guidelines as eGFR ≥60 mL/min/1.73 m(2) with urinary albumin-to-creatinine ratio (UACR) 30-300 mg/g, or eGFR 45-60 mL/min/1.73 m(2) with UACR <30 mg/g. Multivariate logistic regression was used to assess the association between RDW and early kidney injury, adjusting for demographic, socioeconomic, and clinical confounders (age, sex, race, education, poverty index, hypertension, diabetes). Receiver operating characteristic curves were applied to determine the optimal RDW cutoff, and restricted cubic spline (RCS) models were used to explore dose-response relationships. RESULTS: After adjusting for confounders, there is a positive correlation between RDW and early kidney injury (OR = 1.26, 95% CI: 1.08-1.45, p = 0.013). RDW quartile analysis showed that the highest quartile group (>13.1%) had a 1.74-fold risk compared to the lowest group (<12.1%) (95% CI: 1.27-2.40, p < 0.001). RCS confirmed a nonlinear dose-response relationship (nonlinear p < 0.05). The area under the curve for RDW predicting early kidney injury was 0.86. At the optimal cutoff value of 12.7%, sensitivity was 87.5% and specificity was 71.42%. In the hypertensive population (n = 1,190), RDW still significantly predicted early kidney injury (OR = 1.26, 95% CI: 1.10-1.47, p = 0.007). CONCLUSION: Elevated RDW is significantly associated with the risk of early kidney injury and is robust in the hypertensive population. RDW > 12.7% can serve as an economical and convenient screening threshold, especially suitable for early risk stratification of high-risk groups in resource-limited areas. Future prospective studies are needed to validate its causal mechanism and clinical utility.