Background and Aims

Intermittently Scanned Continuous Glucose Monitoring (isCGM) provides new glucometrics as the percentage of time-in-range (TIR) and variability measures (standard deviation (SD), Coefficient of Variation (CV)) to evaluate glycemic control beyond classical HbA1c. Although TIR has been related with microvascular complication development due to its good correlation to HbA1C, this relationship could be altered under high glycemic variability (GV). The aim of the present study is to evaluate the correlation between TIR and HbA1c in this situation.

Methods

Prospective observational study in T1DM patients under isCGM and intensive insulin therapy (insulin pumps (IP) or multiple daily injections). HbA1C, TIR, SD and CV were analyzed by linear regression analysis and Pearson’s correlation coefficient. Treatment modality and demographic variables were also recorded.

Results

146 patients were studied (age range 4-65 years,49.3% pediatric, 46% females, average HbA1c7.1±0.8% and 29.5% IP).

A strong correlation between TIR and HbA1c(R=-0.744;R2=0.544, p<0.001) was found, so, for every absolute 10% change in TIR, there was a 0.7% change in HbA1C. However, this correlation was higher in low GV patients (CV<35) (R=-0.914;R2=0.836) than in those with high variability index (R=-0.549;R2 = 0.301),p<0.001. The same correlation was found in pediatric population(<16 years old), and stratified by SD. Nonetheless, treatment modality did not show any significant differences between groups.

Conclusions

Although TIR has a strong correlation with HbA1c, this relationship is weakened in high variability patients defined by CV or SD. Thus, TIR should be used as the preferred metric beyond HbA1c only in low GV subpopulations.