(FRONTLINE MEDICAL NEWS) A 6-month course of continuous glucose monitoring modestly cut hemoglobin A1c levels in patients with type 1 diabetes who used multiple daily insulin injections, according to two separate randomized trials reported online Jan. 24 in JAMA.

Compared with usual care, continuous glucose monitoring decreased mean HbA1c levels by 0.6% in a multicenter open-label U.S. study involving 158 participants and by 0.4% in a multicenter open-label crossover trial in Sweden. Both research groups noted that lengthier trials are needed to assess longer-term effectiveness of continuous glucose monitoring in this patient population, the possible adverse effects of long-term use, and whether the reduction in HbA1c levels translates into improved clinical outcomes.

The first trial, which was conducted at 24 U.S. endocrinology practices, involved patients aged 25 and older (mean age, 48 years) who had had type 1 diabetes for a median of 19 years and whose baseline HbA1c levels ranged from 7.5% to 10%. A total of 105 of these participants were randomly assigned to use continuous glucose monitoring (CGM group) and 53 to receive usual care (control group) for 24 weeks, said Roy W. Beck, MD, PhD, of the Jaeb Center for Health Research, Tampa, and his associates.

The CGM group was instructed to wear the device on at least 85% of days and to calibrate it at least twice per day, and they were to verify their glucose level by doing blood glucose meter testing at least three times daily before injecting insulin. The control group was instructed to do blood glucose meter testing at least four times per day.

The primary outcome, reduction in HbA1c level, was 1.1% at 12 weeks and 1% at 24 weeks with CGM, compared with 0.5% at 12 weeks and 0.4% at 24 weeks with usual care. At the end of the treatment period, the mean difference between the two study groups in HbA1c reduction was 0.6%.

Secondary outcomes also favored CGM, including the time spent with glucose levels within the target range of 70-180 mg/dL, duration of hypoglycemia, duration of hyperglycemia, and glycemic variability. In addition, patients reported a high level of satisfaction with CGM, Dr. Beck and his associates said (JAMA. 2017 Jan 24. doi: 10.1001/jama.2016.19975).

The second trial was conducted at 15 medical centers in Sweden and involved 161 adults aged 18 and older (mean age, 44 years) whose baseline HbA1c levels were 7.5% or higher. The participants served as their own controls, randomly assigned to use either CGM or usual care for 26 weeks and then to crossover to the other group for 26 weeks, said Marcus Lind, MD, PhD, of the diabetes outpatient clinic, Uddevalla (Sweden) Hospital, and his associates.

The primary outcome, reduction in HbA1c level, was lower by 0.4% with CGM than with usual care. In addition, secondary outcomes also favored CGM, including treatment satisfaction, patient concern about having a hypoglycemic episode, overall well-being, and mean glucose levels. However, in this study, patients measured their blood glucose levels less often with CGM (2.7 measurements per day) than with usual care (3.7 measurements per day).

One patient developed an allergic reaction to the device’s internal sensor and had it removed, according to Dr. Lind and his associates (JAMA. 2017 Jan 24. doi: 10.1001/jama.2016.19976).

Dr. Beck’s study was sponsored by Dexcom, maker of the CGM device, which also participated in designing the study, writing the protocol, reviewing and approving the manuscripts, and interpreting the data. Dr. Beck reported financial relationships with Dexcom and Abbott Diabetes Care, and his associates reported ties to numerous industry sources. Dr. Lind’s study was sponsored by the NU Hospital Group and Dexcom. Dr. Lind reported financial relationships with AstraZeneca, Dexcom, Eli Lilly, Medtronic, Novo Nordisk, and Rubin Medical, and his associates reported ties to numerous industry sources.