Diabetes Q&A

New Studies Compare Continuous Glucose Monitoring with Standard Care in Patients with Type 1 Diabetes

In the current issue of JAMA, 2 studies reported on the use of continuous glucose monitoring (CGM) devices in patients with type 1 diabetes who use multiple daily insulin shots. Their findings showed modest improvements in hemoglobin A1c (HbA1c) levels compared to standard, self-monitored glucose management.

Prior studies found that CGM benefited participants with insulin pumps but little information is available on potential benefits to patients with type 1 diabetes, most of whom use insulin injections.
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According to the research team that published “Continuous Glucose Monitoring vs Conventional Therapy for Glycemic Control in Adults with Type 1 Diabetes treated with multiple daily insulin injections: the GOLD randomized clinical trial” (the GOLD trial), “the majority of individuals with type 1 diabetes do not meet recommended glycemic targets.” Both studies hypothesized that CGM would assist patients and improve HbA1c levels.

In the GOLD trial, researchers randomly assigned 161 patients to receive standard care for monitoring glucose levels or a CGM device. The mean age of participants was 43.7 years, 45.3% were women, and the mean HbA1c was 8.6%. Participants received treatment for 26 weeks, which was followed by a 17-week washout period. Researchers compared HbA1c levels between the groups at 26 weeks.

The mean HbA1c was 7.92% during CGM use and the mean HbA1c during conventional treatment was 8.35%. The average difference between the 2 treatments was -4.7, or .43%.

“Of 19 secondary end points comprising psychosocial and various glycemic measures, 6 met the hierarchical testing criteria of statistical significance, favoring continuous glucose monitoring compared with conventional treatment,” the researchers wrote.

Overall, 5 patients in the standard care group had severe hypoglycemia, and only 1 patient in the CGM group had severe hypoglycemia.

The GOLD trial indicated that CGM may be beneficial for patients with type 1 diabetes treated with multiple daily insulin injections compared to traditional treatment. Likewise, the researchers who published “Effect of continuous glucose monitoring on glycemic control in adults with type 1 diabetes using insulin injections: the DIAMOND Randomized clinical trial” (the DIAMOND trial) found similar results.

The DIAMOND trial included 158 adults with type 1 diabetes who had HbA1c levels from 7.5% to 9.9%. Fifty-three participants were randomly assigned to the usual care group, and 105 participants were assigned to the CGM group. The mean age of participants in the DIAMOND trial was 48 years, 44% of whom were women, and the mean baseline HbA1c level was 8.6%. The median diabetes duration for participants was 19 years.

Researchers measured changes in HbA1c level from baseline to 24 weeks, and had 18 secondary end points.

Participants in the CGM group used CGM for 6 days a week or more in month 6. The mean HbA1c reduction from baseline to 12 weeks was 1.1%, and at 24 weeks was 1.0%. The control group had a mean HbA1c reduction from baseline to 12 weeks of 0.5%, and of 0.4% at 24 weeks. The adjusted treatment-group difference in mean change of HbA1c level from baseline to 24 weeks was -0.6%.

“Median duration of hypoglycemia at <70 mg/dL was 43 min/d (IQR, 27-69) in the CGM group vs 80 min/d (IQR, 36-111) in the control group (P = .002),” the researchers stated.

In each group, 2 participants had severe hypoglycemia events.

Taken together, the trials show that CGM may be beneficial for glucose monitoring in type 1 diabetes patients. The decrease HbA1c levels in patients on CGM was small but did show improvement compared to standard care.

However, an editorial published in the same issue by Dr Mayar Davidson at the Charles R. Drew University of Medicine and Science noted several conditions that may impact the use of CGM as a widespread method for monitoring glucose levels.

According to Dr Davidson, CGM are invasive and “the favorable results observed among motivated patients who participate in clinical trials may be less robust than outcomes among patients in routine clinical practice.” In addition, CGM are expensive and the limited results and short trial period in the 2 studies might not persuade insurance providers to cover the cost of CGM.

Further research is needed to examine the long-term harm and benefits of CGM devices, and additional studies would need to show significant improvement between CGM and standard care for monitoring glucose levels to make the cost, both financially and physically, worthwhile for patients.

—Melissa Weiss

Reference:

  1. Beck RW, Riddlesworth T, Ruedy K, et al. Effect of continuous glucose monitoring on glycemic control in adults with type 1 diabetes using insulin injections: the DIAMOND Randomized clinical trial [published online January 24, 2017]. JAMA 317 (4): 371-378.
  2. Lind M, Polonsky W, Hirsch IB, et al. Continuous glucose monitoring vs conventional therapy for glycemic control in adults with type 1 diabetes treated with multiple daily insulin injections: the GOLD randomized clinical trial [published January 14, 2017]. JAMA 317 (4): 379-387.
  3. Davidson, MB. Continuous glucose monitoring in patients with type 1 diabetes taking insulin injections. JAMA 317 (4): 363-364.