Evaluation of the Association of CGM Metrics with Antihyperglycemic Drugs in Insulin-Treated Diabetics

Abstract

Introduction: Intermittent flash glucose monitoring (FGM) and real-time continuous glucose monitoring (CGM) are used to monitor glycemic excursions for 14 days and can demonstrate time in range (TIR), time above range (TAR), and time below range (TBR). The utility of CGM metrics, such as TIR, TBR, and TAR, in diabetics treated with insulin combined with antihyperglycemic drugs is uncertain. Methods: In a cross-sectional and retrospective study, we investigated the relationship between target metrics from CGM/FGM and HbA1c or glucose variabilities in 80 type 1 and 2 diabetic patients receiving insulin treatment with ≥1 injections per day. The proportions of TIR, TAR, and TBR from FGM in relation to HbA1c and coefficient of variation (CV)% in types 1 and 2 diabetics were analyzed. Multivariable analyses were performed regarding the associations of TIR with biochemical factors and glycemic variabilities. TBR was also examined in relation to antidiabetic agents and diabetic type in multiple regression analyses. Finally, the association of retinopathy with FGM-CGM metrics was examined using a logistic analysis. Results: When patients were grouped by sex and diabetic type, significant differences in age, TIR, TBR, high-density lipoprotein cholesterol (HDLC), and insulin dose were detected using Kruskal-Wallis analyses. HbA1c significantly correlated with TIR (p < 0.001) and TAR (p < 0.001) using Pearson’s correlation analysis. TBR significantly correlated with CV% (p < 0.001). Multivariable analysis of TIR showed a significant negative association with HbA1c (p = 0.02). Incretin combined with insulin therapy reduced the TBR proportion significantly according to the multivariate analysis. Retinopathy tended to be related to HbA1c (p = 0.059) and duration (p = 0.078) but not TIR (p = 0.891), according to the logistic analysis. Conclusions: These results demonstrate that CGM metrics reflect glucose control for 2 weeks using TIR. In addition, combined therapy with incretin and insulin therapy is superior for reducing hypoglycemia, based on TBR. Thus, TBR is also useful for monitoring hypoglycemia. However, FGM/CGM metrics do not predict retinopathy accurately.