Benefits of a Switch from Intermittently Scanned Continuous Glucose Monitoring (isCGM) to Real-Time (rt) CGM in Diabetes Type 1 Suboptimal Controlled Patients in Real-Life: A One-Year Prospective Study §

Abstract

The switch from intermittently scanned continuous glucose monitoring (isCGM) to real-time (rt) CGM could improve glycemic management in suboptimal controlled type 1 diabetes patients, but long-term study is lacking. We evaluated retrospectively the ambulatory glucose profile (AGP) in such patients after switching from Free Style Libre 1 (FSL1) to Dexcom G4 (DG4) biosensors over 1 year. Patients (n = 21, 43 ± 15 years, BMI 25 ± 5, HbA1c 8.1 ± 1.0%) had severe hypoglycemia and/or HbA1c ≥ 8%. AGP metrics (time-in-range (TIR) 70-180 mg/dL, time-below-range (TBR) <70 mg/dL or <54 mg/dL, glucose coefficient of variation (%CV), time-above-range (TAR) >180 mg/dL or >250 mg/dL, glucose management indicator (GMI), average glucose) were collected the last 3 months of FSL1 use (M0) and of DG4 for 3, 6 (M6) and 12 (M12) months of use. Values were means ± standard deviation or medians [Q1;Q3]. At M12 versus M0, the higher TIR (50 ± 17 vs. 45 ± 16, p = 0.036), and lower TBR < 70 mg/dL (2.5 [1.6;5.5] vs. 7.0 [4.5;12.5], p = 0.0007), TBR < 54 mg/dL (0.7 [0.4;0.8] vs. 2.3 [0.8;7.0], p = 0.007) and %CV (39 ± 5 vs. 45 ± 8, p = 0.0009), evidenced a long-term effectiveness of the switch. Compared to M6, TBR < 70 mg/dL decreased, %CV remained stable, while the improvement on hyperglycemia exposure decreased (higher GMI, TAR and average glucose). This switch was a relevant therapeutic option, though a loss of benefit on hyperglycemia stressed the need for optimized management of threshold alarms. Nevertheless, few patients attained the recommended values for AGP metrics, and the reasons why some patients are "responders" vs. "non-responders" warrant to be investigated.

Keywords: glucose biosensors; hypoglycemia; insulin resistance; intermittently scanned continuous glucose monitoring; real-time continuous glucose monitoring; type 1 diabetes.

Figure 1

Study design. Abbreviations: AGP, Ambulatory Glucose Profile; BMI, body mass index; eGDR, estimated glucose disposal rate; FSL1, FreeStyle Libre version 1; DG4, Dexcom G4 platinum; HbA1c, plasma glycated hemoglobin A1c; T1D, type 1 diabetes.

Figure 2

Box-and-whisker plot of changes in TIR (A), TBR < 70 mg/dL (B), TBR < 54 mg/dL (C) and glucose %CV (D). Data represented as plots are median, first quartile (Q1 or 25th percentile) and third quartile (Q3 or 75th percentile), min and max, mean (as a cross) and all individual points for changes calculated from DG4 parameter at M3 or M6 or M12 − FSL1 parameters expressed as percentage points. Values indicated are means ± SD or median [Q1;Q3]. Data are from 21 T1D followed-up patients. Abbreviations: %CV, glucose % coefficient of variability; DG4, Dexcom platinum G4; FSL1, FreeStyle Libre version 1; TBR, time-below-range; TIR, time-in-range.

Figure 3

Box-and-whisker plot of changes in TAR > 180 mg/dL (A), TAR > 250 mg/dL (B), average IG concentration mg/dL (C) and GMI % (D). Data represented as plots are median, first quartile (Q1 or 25th percentile) and third quartile (Q3 or 75th percentile), min and max, mean (as a cross) and all individual points for changes calculated from DG4 parameter at M3 or M6 or M12 − FSL1 parameters expressed as percentage points except for average IG concentration which is in mg/dL. Values indicated are means ± SD or median [Q1;Q3]. Data are from 21 T1D followed-up patients. Abbreviations: DG4, Dexcom platinum G4; FSL1, FreeStyle Libre version 1; GMI, glucose management indicator; IG, interstitial glucose; TAR, time-above-range.

Figure 4

Linear association between changes obtained after switching from FSL1 to DG4 at M12 for TIR with TAR > 180 mg/dL (A) or with TAR > 250 mg/dL (B), and for glucose %CV with TBR < 70 mg/dL (C) or with TBR < 54 mg/dL (D). Changes were calculated from DG4 12-month parameters − FSL1 last 3-month parameters (values at M12 − values at M0) in 21 T1D patients and are expressed as percentage points. Correlation analysis was performed using Spearman’s rank correlation coefficient denoted by “r” for rho on the figure (p < 0.05). Equation of the line for A or B: change in TAR > 180 mg/dL= −1.02 × [change in TIR] + 5.43; change in TAR > 250 mg/dL = −0.52 × [change in TIR] + 2.20. Equations of the lines for C or D: change in TBR < 70 mg/dL = 0.65 × [change in %CV] − 1.16; change in TBR < 54 mg/dL = 0.43 × [change in %CV] − 0.24. Abbreviations: %CV, glucose coefficient of variability; DG4, Dexcom platinum G4; FSL1, FreeStyle Libre version 1; T1D, type 1 diabetes; TBR, time-below-range; TIR, time-in-range; TAR, time-above-range. No association was found between the number of scan/d with FSL1 at M0 and the evolution of metrics with DG4 over 12 months of follow-up.