The HbA1c/GMI Ratio Does Not Independently Predict Diabetic Retinopathy in Adults with Type 1 Diabetes: A Multicenter Cross-Sectional Study

The discordance between glycated haemoglobin (HbA1c) and the glucose management indicator (GMI) has been proposed as a marker of vascular risk in diabetes. This study evaluated whether the HbA1c/GMI ratio independently predicts diabetic retinopathy (DR) in adults with type 1 diabetes (T1D) using continuous glucose monitoring. We conducted a multicenter cross-sectional study involving 1,070 adults using flash glucose monitoring. Participants were stratified as high glycators (ratio > 0.9) or non-high glycators based on the HbA1c/GMI ratio. DR status was assessed by ophthalmologic evaluation. Multivariable logistic regression and 1:1 propensity score matching were used to assess independent associations with DR, adjusting for age, sex, diabetes duration, smoking, hypertension, LDL cholesterol, BMI, and insulin dose. While high glycators had a higher crude DR prevalence (31.3% vs. 23.1%, p = 0.020), the HbA1c/GMI ratio was not independently associated with DR in adjusted models (OR 1.19; 95% CI: 0.34–4.15; p = 0.785) or in the matched cohort (OR 1.23; 95% CI: 0.76–1.99; p = 0.391). Absolute HbA1c remained the strongest glycemic predictor. These findings suggest that the HbA1c/GMI ratio may aid in interpreting discordant glycemic profiles but lacks independent prognostic value for DR.