Associations between A1C and Continuous Glucose Monitoring–Derived Glycemic Parameters

Abstract

The percentage of continuous glucose monitoring (CGM)-derived sensor glucose (SG) values in the 70-180 mg/dL range (time in range [TIR]) is an important outcome for patients and their clinicians; however, consensus TIR goals are lacking. This study aimed to characterize associations between CGM-derived glycemic metrics and A1C in 4 clinical trials: DIAMOND Phase 1 (N=104), DIAMOND Phase 2 (N=69), REPLACE-BG (N=216), and HypoDE (N=141). Each study lasted ≥24 weeks, used current-generation CGM systems (Dexcom, Inc.), and included comparisons of central-lab end-of-study A1C to CGM data during the preceding 3 mo. Data from 530 adults with diabetes (455 type 1) were analyzed. The Figure shows mean SG (MSG), TIR, time <70, <54, and >250 mg/dL for individuals in 6 A1C bins. Higher A1C bins were associated with higher MSG and lower TIR; lower A1C bins were associated with lower MSG and higher TIR. For subjects with A1C <7.0%, median TIR was 72%, with 90% of subjects having TIR >57%. Median time with SG <54 mg/dL was <20 min/day for all A1C bins, but median time with SG >250 mg/dL increased from 0.6 h/day to 6.7 h/day across bins. For subjects with A1C ≥8.0%, median TIR was 44%, with 90% of the subjects having TIR <59%. In CGM users, low A1C values can be achieved with minimal additional exposure to very low SG values. The observed associations between TIR and A1C may help clinicians and patients establish appropriate TIR goals. Disclosure P. Calhoun: Employee; Self; Dexcom, Inc.. Stock/Shareholder; Self; Dexcom, Inc.T. Johnson: Employee; Self; Dexcom, Inc.J. Welsh: Employee; Self; Dexcom, Inc.. Stock/Shareholder; Self; Dexcom, Inc., Medtronic. T.C. Walker: Employee; Self; Dexcom, Inc.D.A. Price: Employee; Self; Dexcom, Inc..