Association between HbA1c and red cell distribution width-standard deviation in newly diagnosed, treatment-naïve type 2 diabetes mellitus: a retrospective cross-sectional study.

Authors

Kemal Ozan Lule, Anil Beyaz, Hamit Yildiz

Published in

BMC endocrine disorders. Jul 04, 2026. Epub Jul 04, 2026.

Abstract

Red cell distribution width-standard deviation (RDW-SD), a measure of erythrocyte volume heterogeneity, has attracted increasing interest as a hematologic marker linked to inflammation, oxidative stress, and metabolic dysfunction beyond anemia evaluation. However, evidence on the relationship between glycated hemoglobin (HbA1c) and RDW-SD in newly diagnosed, treatment-naïve type 2 diabetes mellitus (T2DM) remains limited. This study investigated the association between HbA1c and RDW-SD after accounting for hematologic, nutritional, renal, and metabolic factors that are routinely available at diagnosis.
In this retrospective cross-sectional study, 202 adults aged 18-65 years with newly diagnosed, treatment-naïve T2DM were evaluated at a tertiary university hospital between September 2024 and January 2026. Patients with anemia, mean corpuscular volume abnormalities, advanced renal impairment, acute inflammation or infection, recent transfusion, prior antidiabetic therapy, active bleeding, or hematologic malignancy were excluded. Associations between HbA1c and RDW-SD were examined using correlation, partial correlation, and hierarchical linear regression analyses. Additional analyses assessed RDW-SD across HbA1c tertiles and tested the robustness of the association after inclusion of fasting glucose.
HbA1c showed a positive correlation with RDW-SD (r = 0.664, p < 0.001), which remained essentially unchanged after adjustment for age, sex, body mass index, hemoglobin, mean corpuscular volume, creatinine, ferritin, and vitamin B12 (partial r = 0.662, p < 0.001). Mean RDW-SD increased stepwise across ascending HbA1c tertiles (40.40 ± 3.04, 42.96 ± 3.38, and 46.13 ± 3.85 fL; p-trend < 0.001). In hierarchical regression, HbA1c produced the largest incremental gain in explained variance (ΔR² = 0.323, p < 0.001) and remained the strongest correlate of RDW-SD in the fully adjusted model (B = 1.535, β = 0.674, p < 0.001). In sensitivity analysis, the association persisted after additional adjustment for fasting glucose.
In newly diagnosed, treatment-naïve T2DM, higher HbA1c levels were associated with greater RDW-SD. These findings are hypothesis-generating and do not establish RDW-SD as a clinical marker of glycemic burden or dysglycemia assessment.
Not applicable.

PMID:
42401886
Bibliographic data and abstract were imported from PubMed on 05 Jul 2026.

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