Glycemic Control: CGM vs Self-Monitoring

Continuous glucose monitoring (CGM) for 26 weeks is associated with lower HbA1c than conventional blood glucose self-monitoring in patients with inadequately controlled T1DM, according to a study published online in JAMA.¹

“In this crossover study of persons with type 1 diabetes treated with multiple daily insulin injections, CGM was associated with a mean HbA1c level that was 0.43% (4.7 mmol/mol) less than conventional treatment,” wrote first author Marcus Lind, MD, PhD, of the Uddevala Hospital (Uddevalla, Sweden), and colleagues.

A HbA1c reduction of 0.3% is usually considered clinically meaningful for decreasing long-term diabetic complications, according to the authors.

The study is also the first to link CGM with significant improvement in several psychosocial variables, compared to conventional therapy.

Because CGM delivers continuous reports of glucose levels and trends, this method would seem to provide an advantage to self-monitoring of blood glucose. However, clinical trials have produced mixed results about the effectiveness of CGM on glycemic control. Results have varied depending on whether CGM is combined with continuous subcutaneous insulin infusions or multiple daily insulin injections. And, clinical trials comparing CGM to conventional therapy have not been conducted until now.

The new study differs from previous trials by including a more general population. It used an open-label crossover design and took place in 15 diabetes outpatient clinics in Sweden between February 24, 2014 and June 2016. The study included participants with T1DM inadequately controlled on multiple daily insulin injections (mean HbA1c 8.6%), excluding individuals with insulin pumps.

Researchers randomized 161 participants (mean age 43.7 years, 45.3% women), to CGM or conventional treatment for 26 weeks, followed by a washout period of 17 weeks during which all patients followed conventional treatment. After that, participants switched groups.

The CGM group was encouraged to use CGM information at least every 1 to 2 hours during daytime. The conventional therapy group was encouraged to self-monitor their blood glucose four or more times per day, according to guidelines.

The main outcome was the difference in HbA1c between weeks 26 and 69 for CGM vs conventional treatment. The study also evaluated diabetes treatment satisfaction, change in satisfaction, well-being, fear of hypoglycemia, and perceived problem areas in diabetes.

The analysis included follow-up data on 142 participants in both treatment periods.

Key results:

• Mean HbA1c:

♦ CGM: 7.92%

♦ Conventional treatment: 8.35%

♦ Mean difference: −0.43% (95%CI, −0.57%to −0.29%, P<0.001)

• Total daily insulin dose:

♦ CGM: 56.5 U

♦ Conventional treatment: 57.8 U

• Wellbeing, treatment satisfaction, and fear of hypoglycemia improved with CGM

• Mean percentage of time in hypoglycemia range (<70 mg/dL)

♦ CGM: 2.79%

♦ Conventional treatment: 4.79%

• Severe hypoglycemia:

♦ CGM: 1 patient

♦ Conventional: 5 patients

♦ Washout period: 7 patients

Improvements in psychosocial variables may be partly due to improvements in HbA1c and decreased time spent in hypoglycemia, according to the authors.

“[T]hese results also suggest that the effectiveness of CGM depends on uninterrupted use during multiple daily insulin injections treatment. Our study increases knowledge in the field of type 1 diabetes in reporting that CGM may be a beneficial option for multiple daily insulin injections-treated patients with respect to HbA1c levels,” they wrote.

They noted that the study could not be blinded, which may have influenced results. And they concluded that more research on clinical outcomes and long-term adverse effects is needed.

Take-home Points

• CGM was associated with a mean HbA1c level that was 0.43% less than conventional self-monitoring in patients with inadequately controlled T1DM on multiple daily insulin injections.

• CGM was also linked to lower total daily insulin dose, and improved wellbeing, treatment satisfaction, and fear of hypoglycemia.

• Mean time spent in hypoglycemia and number of patients affected by severe hypoglycemia were lower for CGM vs conventional treatment.

• More research is needed on clinical outcomes and long-term effects of CGM.

One or more authors reports grants, consulting, honoraria, personal and lecture fees, advisory board membership from one or more of the following: AstraZeneca, Dexcom, Novo Nordisk, Rubin Medical, Eli Lilly, Medtronic, Abbott Diabetes Care, Roche, Intarcia, Adocia, BectonDickinson, Biocon, Boehringer Ingelheim, Dance Pharmaceuticals, Eli Lilly, Grünenthal, Gulf Pharmaceuticals, Johnson&Johnson, Marvel, Medimmune, Mylan, Novartis, Roche Diagnostics, Sanofi, Senseonics, ZealandPharma, Insulet, IntegrityApplications,AstraZeneca, Merck, and/or JensenCilag.

Reference: Lind M, 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. JAMA. 2017 Jan 24;317(4):379-387.