Higher HbA1c Than CGM-Derived GMI Linked to Microvascular Complications in Type 1 Diabetes: Study
Type 1 Diabetes
In patients with type 1 diabetes, a laboratory-measured HbA1c level higher than the glucose management indicator (GMI) estimated from continuous glucose monitoring (CGM) was associated with an increased risk of microvascular complications. The findings suggest that the discrepancy between HbA1c and GMI, including their ratio, may help identify high-risk patients and improve risk stratification in routine diabetes care. The study was published in the Diabetes Obesity and Metabolism journal by Sandra H. and colleagues.
To establish whether the GMI/HbA1c ratio acts as an independent predictor of microvascular disease, a multi-center observational cross-sectional study was done. In this study, 1,315 adult participants with T1D with a disease duration of at least 5 years using continuous glucose monitoring with a sensor coverage rate of ≥80% for the past 56 days before laboratory HbA1c measurement were recruited.
The participants were grouped into tertiles according to the GMI/HbA1c ratio: high glycators (lowest ratio, where laboratory HbA1c is significantly higher than the estimated glucose), intermediate glycators, and low glycators (highest ratio, where laboratory HbA1c is lower than estimated glucose). Multivariable logistic regression models were used to determine the independent predictors of microvascular complications, diabetic retinopathy, nephropathy, and neuropathy.
Key findings:
- Analysis across the 1,315 participants with T1D revealed marked clinical, glucometric, and complication rate disparities across GMI/HbA1c ratio tertiles.
- High glycators were significantly older than intermediate and low glycators (55.4 vs. 53.4 vs. 50.8 years; p < 0.001).
- High glycators exhibited lower average glucose (156.3 vs. 161.8 vs. 166.1 mg/dL; p < 0.001), higher time in range (66.3% vs. 62.9% vs. 59.9%; p < 0.001), higher time in tight range (42.9% vs. 39.9% vs. 37.1%; p < 0.001), lower glucose coefficient of variation (34.5% vs. 34.9% vs. 35.6%; p = 0.023), lower GMI (7% vs. 7.2% vs. 7.3%; p < 0.001), but markedly higher laboratory HbA1c (8.1% vs. 7.3% vs. 6.6%; p < 0.001).
- The overall prevalence of grouped microvascular complications was significantly higher in high glycators compared to intermediate and low glycators (38.9% vs. 28.2% vs. 23.7%; p < 0.001).
- Specific complication rates were also highest in high glycators: ocular disease (31% vs. 20.2% vs. 19.7%; p < 0.001), diabetic nephropathy (14.9% vs. 8.3% vs. 6.2%; p < 0.001), and diabetic polyneuropathy (10.6% vs. 6.8% vs. 3.4%; p < 0.001).
- After full adjustment for clinical and glucometric variables, the GMI/HbA1c ratio remained significantly associated with reduced odds of composite microvascular complications (OR 0.71; 95% CI: 0.61–0.81; p < 0.001) and ocular disease (OR 0.71; 95% CI: 0.61–0.82; p < 0.001).
In summary, results from multicenter observational studies show that the GMI/HbA1c ratio is strongly correlated with the occurrence of microvascular complications among Type 1 diabetics. These findings are significant because they show that the computation of the ratio can be used to determine the clinical utility of identifying at-risk patients and setting individual glycemic targets.
Reference:
S. Herranz-Antolín, M. A. Martínez-Brocca, G. Cánovas-Molina, et al., “ Association Between the GMI/HbA1c Ratio and Microvascular Complications in Type 1 Diabetes: A Multicenter Cross-Sectional Study,” Diabetes, Obesity and Metabolism (2026): 1–12, https://doi.org/10.1111/dom.71385.
