Continuous Glucose Monitoring Variables and HbA1c in Children and Adolescents with Type 1 Diabetes

Objective: Associations between Continious Glucose Monitoring (CGM) variables (metrics) and HbA_1c is not well understood. In this exploratory study we assessed the association between mean sensor glucose (mean CGM) and HbA_1c and how it is affected by sensor type (real-time CGM vs. intermittent scanned CGM), patient characteristics, and other CGM variables in children and adolescents with type 1 diabetes.

Methods: Data were obtained from Swedish paediatric diabetes quality registry (SWEDIABKID) and Diasend. Paired HbA_1c and CGM data collected within one year were analyzed, including a maximum of four individual HbA_1c at least 2 months apart and for which CGM data were available for 12 weeks prior to HbA_1c.

Results: 174 children were included of whom 141 had a diabetes duration ≥ 1-year; 71 used real-time CGM and 70 used intermittent scanned CGM. The intermittent scanned CGM children were older, had a higher proportion of children on insulin injections versus pump, and more CGM recordings during an 8-week registration. A stronger correlation between HbA_1c and mean CGM was observed based on a sensor period ≥ 8 weeks preceding HbA_1c in children with ≥ 1-year diabetes duration (r= 0.70, p<0.01). HbA_1c was more weakly correlated with Time In Range (r=-0.40, p<0.01). Low HbA_1c and low CGM Standard Deviation and, for intermittent scanned CGM, higher daily sensor duration was associated with a stronger correlation between mean CGM and HbA_1c. HbA_1c was dependent on Time Above Range and Time Below Range in intermittent scanned CGM users while in real-time CGM only Time Above Range impacted.

Conclusions: HbA_1c correlated only moderately with mean CGM and discrepancies should be expected for the child with short diabetes duration, high HbA_1c or high CGM Standard Deviation.