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Original Investigation
June 2, 2021

Effect of Continuous Glucose Monitoring on Glycemic Control in Patients With Type 2 Diabetes Treated With Basal Insulin: A Randomized Clinical Trial

Author Affiliations
  • 1International Diabetes Center, Park Nicollet Internal Medicine, Minneapolis, Minnesota
  • 2Jaeb Center for Health Research, Tampa, Florida
  • 3Keck School of Medicine of the University of Southern California, Los Angeles
  • 4University of Michigan, Ann Arbor
  • 5Scripps Whittier Diabetes Institute, San Diego, California
  • 6Vanderbilt University Medical Center, Nashville, Tennessee
  • 7Emory University School of Medicine, Atlanta, Georgia
  • 8Henry Ford Health System, Detroit, Michigan
  • 9Iowa Diabetes Research, West Des Moines
  • 10University of North Carolina School of Medicine, Chapel Hill
  • 11Washington University School of Medicine, St Louis, Missouri
  • 12Feinberg School of Medicine, Northwestern University, Chicago, Illinois
  • 13Las Vegas Endocrinology, Henderson, Nevada
  • 14Carteret Medical Group, Morehead City, North Carolina
  • 15Amarillo Medical Specialists, Amarillo, Texas
  • 16Diabetes & Endocrinology Consultants PC, Morehead City, North Carolina
  • 17Behavioral Diabetes Institute, San Diego, California
  • 18Dexcom Inc, San Diego, California
  • 19International Diabetes Center, HealthPartners Institute, Minneapolis, Minnesota
JAMA. 2021;325(22):2262-2272. doi:10.1001/jama.2021.7444
Key Points

Question  For adults with poorly controlled type 2 diabetes treated with basal insulin without prandial insulin in primary care practices, does continuous glucose monitoring improve hemoglobin A1c (HbA1c) levels compared with blood glucose meter monitoring?

Findings  In a randomized clinical trial including 175 adults with type 2 diabetes, there was a significantly greater decrease in HbA1c level over 8 months with continuous glucose monitoring than with blood glucose meter monitoring (−1.1% vs −0.6%).

Meaning  Continuous glucose monitoring resulted in better glycemic control compared with blood glucose meter monitoring in adults with poorly controlled type 2 diabetes treated with basal insulin without prandial insulin.

Abstract

Importance  Continuous glucose monitoring (CGM) has been shown to be beneficial for adults with type 2 diabetes using intensive insulin therapy, but its use in type 2 diabetes treated with basal insulin without prandial insulin has not been well studied.

Objective  To determine the effectiveness of CGM in adults with type 2 diabetes treated with basal insulin without prandial insulin in primary care practices.

Design, Setting, and Participants  This randomized clinical trial was conducted at 15 centers in the US (enrollment from July 30, 2018, to October 30, 2019; follow-up completed July 7, 2020) and included adults with type 2 diabetes receiving their diabetes care from a primary care clinician and treated with 1 or 2 daily injections of long- or intermediate-acting basal insulin without prandial insulin, with or without noninsulin glucose-lowering medications.

Interventions  Random assignment 2:1 to CGM (n = 116) or traditional blood glucose meter (BGM) monitoring (n = 59).

Main Outcomes and Measures  The primary outcome was hemoglobin A1c (HbA1c) level at 8 months. Key secondary outcomes were CGM-measured time in target glucose range of 70 to 180 mg/dL, time with glucose level at greater than 250 mg/dL, and mean glucose level at 8 months.

Results  Among 175 randomized participants (mean [SD] age, 57 [9] years; 88 women [50%]; 92 racial/ethnic minority individuals [53%]; mean [SD] baseline HbA1c level, 9.1% [0.9%]), 165 (94%) completed the trial. Mean HbA1c level decreased from 9.1% at baseline to 8.0% at 8 months in the CGM group and from 9.0% to 8.4% in the BGM group (adjusted difference, −0.4% [95% CI, −0.8% to −0.1%]; P = .02). In the CGM group, compared with the BGM group, the mean percentage of CGM-measured time in the target glucose range of 70 to 180 mg/dL was 59% vs 43% (adjusted difference, 15% [95% CI, 8% to 23%]; P < .001), the mean percentage of time at greater than 250 mg/dL was 11% vs 27% (adjusted difference, −16% [95% CI, −21% to −11%]; P < .001), and the means of the mean glucose values were 179 mg/dL vs 206 mg/dL (adjusted difference, −26 mg/dL [95% CI, −41 to −12]; P < .001). Severe hypoglycemic events occurred in 1 participant (1%) in the CGM group and in 1 (2%) in the BGM group.

Conclusions and Relevance  Among adults with poorly controlled type 2 diabetes treated with basal insulin without prandial insulin, continuous glucose monitoring, as compared with blood glucose meter monitoring, resulted in significantly lower HbA1c levels at 8 months.

Trial Registration  ClinicalTrials.gov Identifier: NCT03566693

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