The Effect of Reduced Self-Monitored Blood Glucose Testing After Adoption of Continuous Glucose Monitoring on Hemoglobin A1c and Time in Range

Abstract

The effectiveness of real-time continuous glucose monitoring (rtCGM) in adults with diabetes treated with insulin injections was evaluated in the 24-week DIAMOND clinical trial comparing rtCGM users to a control group using self-monitored blood glucose (SMBG) testing ( Clinicaltrials.gov : NCT02282397). All participants were instructed to use SMBG results for diabetes management decisions; however, SMBG testing frequency varied within the rtCGM group. This brief report evaluated how SMBG frequency changes in the rtCGM group were correlated with glycemic outcomes in the same trial. Baseline and end-of-study hemoglobin A1c (HbA1c) levels, percentages of CGM values in the 70-180 mg/dL target range (time in range [TIR]), mean of daily differences (MODD), and glycemic coefficients of variation (CVs) were compared. The rtCGM group analyzed included 175 participants-99 with type 1 diabetes (T1D) and 76 with type 2 diabetes (T2D). When comparing participants whose SMBG testing frequency decreased by >1/day versus ≤1/day, mean change in HbA1c was similar (-0.9 ± 0.7 percentage points in both groups, P = 0.59), as was change in TIR (+3.9 ± 14.3 vs. +5.7 ± 13.7 percentage points, respectively, P = 0.39). Likewise, when comparing participants in the highest and lowest quartiles of SMBG frequency reduction (≥2.2 vs. ≤0.4 fewer tests/day, respectively), changes in HbA1c (-0.8 ± 0.6 vs. -0.9 ± 0.6 percentage points, respectively, P = 0.52) and TIR (+4.8 ± 13.2 vs. +5.6 ± 12.7 percentage points, respectively, P = 0.98) were similar. The mean (standard deviation [SD]) change in MODD was -8.3 mg/dL (14.8) and -5.5 mg/dL (14.7) for participants who reduced their SMBG frequency by >1 test/day and ≤1 test/day, respectively; the mean (SD) change in CV was -3.6% (5.0) and -1.6% (5.1) for participants who reduced their SMBG frequency by >1 test/day and ≤1 test/day, respectively. These findings suggest that individuals who decrease the frequency of SMBG testing can effectively base some of their diabetes-related treatment decisions on glucose concentrations, trend information, and alarms provided by their rtCGM systems.

Keywords: CGM; Glycemic control; HbA1c; SMBG reduction; nonadjunctive.