The Relationship Between HbA1c and GMI and Glucose Metrics in Children and Adolescents with Type 1 Diabetes Using AID

HbA1c remains the standard biomarker for long-term glycemic control, but it lacks precision in capturing short-term glucose variability and acute excursions. This limitation is especially relevant in children with type 1 diabetes (T1D) who use continuous glucose monitoring systems (CGMS) and automated insulin delivery (AID) systems.

Aim

To evaluate the temporal relationship between HbA1c and the glucose management indicator (GMI), and their associations with CGMS-derived glycemic parameters over 12-weekperiod in children and adolescents with T1D using AIDsystems.

Material-methods

In this retrospective cross-sectional observational study,81 children and adolescents with T1D on the Medtronic MiniMed 780G™ system were included.CGMS data covering 12weeks prior to HbA1c measurement were analyzed in two-week intervals.Correlations between HbA1c,GMI, andCGMS metrics were assessed

Results

HbA1c was positively correlated with all GMI values,with the strongest correlation observed for the last six-weekGMI (r=0.728,p<0.001). The mean difference between HbA1c and last12-weekGMI was0.57% (95%CI:-1.13to 2.27).GMI demonstrated stronger correlations than HbA1c with time in range (TIR),time above range(TAR),and time below range(TBR).Notably, in individuals with similar TIR (~70%), HbA1c values varied widely (6.6–9.6% /48-81mmol/mol),while GMI remained stable (6.8–7.1%).

Discussion

HbA1c exhibited the strongest correlation with GMI calculated over the last six weeks,suggesting that it primarily reflects recent glycemic trends rather than cumulative exposure.GMI also showed closer alignment with CGMS-derived indices such as TIR,TAR,and TBR,indicating its enhanced sensitivity in capturing day-to-day glycemic variability,especially in suboptimally controlled individuals.

Conclusion

Given its temporal limitations,HbA1c may not reliably capture 12-weekglycemic patterns in pediatric AIDusers.GMI, as CGMS-derived metric,offers a more consistent and clinically actionable estimate of glycemic control,supporting its integration into routine care for children with T1D.

Keywords:

T1D, AID, CGMS, GMI, sampling period