Real time-glucose monitoring has been around for a decade now to manage blood glucose levels by providing real-time actionable information.

The key treatment end point in type 1 diabetes is the achievement of normal glucose concentrations, without causing hypoglycemia. Patients with type 1 diabetes alter the timing and dosing of insulin to achieve this goal. The majority of patients with type 1 diabetes use daily insulin injections and adjust insulin administration based on their meal timings and the process is often facilitated self-monitored blood glucose (SMBG) values. However, the utility of real-time continuous glucose monitoring (CGM) in improving the management of Type 1 diabetes patients receiving insulin injections has not been well studied in the past. CGM has been compared with SMBG among patients using insulin pumps but not among the large majority of those using insulin injections. CGM definitely can play a positive role in improving diabetes control by limiting hyperglycemia, decreasing episodes of hypoglycemia, lowering glucose variability (although its importance in affecting clinical events has yet to be shown), and enhancing patient satisfaction with glycemic treatment.

In a recent issue of JAMA, two published studies have addressed this lack of data and have thrown light on the use of CGM in type 1 diabetes patients receiving insulin injections. Mayer B. Davidson, MD, professor of medicine at Charles R Drew University and David Geffen School of Medicine, Los Angeles. He wrote an editorial to accompany the two studies, published in JAMA opined that CGM does help in getting a moderate improvement in the A1C, and a little less hypoglycemia in type 1 diabetes patients.

However, there are also a couple of flip sides to this – the device's invasiveness, expense, and a learning curve associated with using it. Besides, the need to use finger pricks for glucose testing is not eliminated.

CGM and Insulin Injections: DIAMOND and GOLD Insights!

DIAMOND Study: (Multiple Daily Injections and Continuous Glucose Monitoring in Diabetes). The study comprised of 158 adults with type 1 diabetes who were using multiple daily insulin injections and had HbA1C levels of 7.5 to 9.9%.

Of these, 105 study participants were allocated to use CGM and 53 to usual care, taking blood glucose readings throughout the day.

After 24 weeks, a modestly high improvement of HbA1c was noted in the CGM group. Patients in the CGM group had a drop in A1C of 1% on average while those in the comparison group dropped an average of 0.4%.

The CGM group also had fewer hypoglycemic episodes—averaging 43 minutes a day, compared to a whopping 80 minutes in the comparison group. The number of severe low blood sugar events was the same, two in each group.

The CGM device showed good acceptability among the patients. About 90% of the patients in the CGM group were were still using it daily, even at the end of six months.

GOLD Study: (Glycemic Control Treated with Multiple Daily Insulin Injections). The study included 161 men and women with type 1 diabetes and an A1C of at least 7.5% who took multiple injections daily. The study patients were allocated to either CGM or conventional treatment for 26 weeks. This was followed by a washout period for 17 weeks before each group switched to the other group for the next phase of the study.

Statistically significantly better HbA1c control was seen with CGM (CGM 7.92% compared to 8.35%). Significantly less hypoglycemic episodes were reported in the CGM group as compared to the conventional monitoring group.

Key Take Home Messages

The fact that CGM has a beneficial effect in managing type 1 diabetes patients using an insulin pump is a well-known fact established through past clinical evidence. However, researchers in the past seemed to have completely discounted the fact that less than 40% of type 1 diabetes patients use pumps and that more than two-thirds of the majority of these patients use insulin injections. Hence, it is imperative to assess and understand the utility of CGM in type 1 diabetic insulin injection users. That’s the knowledge gap tat has got well addressed by these two studies. However, further evaluation and research can bring in better understanding and validation.

Although the two studies did show benefit in the study population, CGM is 'invasive and expensive – and these down-sides need to be factored in while making clinical decisions in a real-world setting.

CGM can be used in and benefit almost anyone with type 1 diabetes. Patients who opt to use CGM need to commit to learn the approach. The responsibility to help patients of type 1 diabetes learn, understand and smoothly adopt CGM, lies on their clinicians who would act as guides and knowledge resources in this context.