Does retrospective continuous glucose monitoring improve HbA1c among adults with type 2 diabetes?

Findings of the GP-OSMOTIC trial

By Dr Amelia Lake

Glycated haemoglobin (HbA1c) is a measure of a person’s average blood glucose levels over the previous ~3 months. General practitioners (GPs) use HbA1c to monitor blood glucose in people with diabetes. However, some report that this metric alone does not provide enough information to support personalised decision-making and collaborative care for people living with type 2 diabetes (T2D). Advanced diabetes technologies, such as continuous glucose monitoring (CGM), can provide more detailed information, and may help GPs and people living with diabetes improve treatment and self-management. However, there is very little research exploring the use of CGM and to guide decision making for people with T2D. The GP-OSMOTIC study (General Practice Optimising Structured MOnitoring To Improve Clinical outcomes in type 2 diabetes) aimed to provide new evidence in this area. This NHMRC-funded study was led by A/Prof John Furler (Department of General Practice, University of Melbourne) and a multidisciplinary team of experts, including members of the ACBRD. 

A total of 299 adults with T2D and an HbA1c above their target, took part in the study. The study used a randomised controlled trial design. Half of the participants were assigned at random to the ‘intervention’ group. They wore a ‘professional-mode’ CGM sensor for 14 days prior to their GP visit and repeated this every 3 months, for 12 months. Participants could not see their glucose data during the 14-day period. At each GP visit, the sensor was removed, and the CGM data were downloaded and discussed (see Figure 1). The other half of the participants became the ‘control’ group. They wore the sensor at baseline and 12 months only and could also not see their glucose data during this time. They attended their usual 3-monthly GP visits and received usual care. At the end of the study, differences were assessed between intervention and control group participants on average HbA1c at 6- and 12 months, time in target glucose range, and diabetes-specific distress. 

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Figure 1: example of daily pattern report which shows glucose levels at 15-minute intervals over a 24-hour period for 15 days.

Findings were published in January 2020 in Lancet Diabetes & Endocrinology. The results were mixed. For example, HbA1c was significantly lower in the intervention group at the 6-month GP visit, but this improvement was not sustained at 12 months. There was also significant increase in the average time in target glucose range, which was sustained over the 12-month period. There was no change in diabetes distress, which was low at baseline and did not increase during the study. 

This was a pragmatic real-world study. This study shows that it is possible to implement advanced diabetes technologies in primary care. The sensor provides a broad range of information, providing the opportunity to support personalised care for adults with T2D in primary care without adverse impact. From a clinical care perspective, although CGM did not change HbA1c in the longer term, there were important short-term benefits. This suggests that use of the sensor as needed may be more useful than repeated wearing on a regular basis. The improved ‘time in range’ is also of interest. It is a relatively new metric and more studies are being published each month, which will help us understand the value of the 12-month improvement seen here. For now, this improvement suggests that use of CGM sensors has the potential to provide insights into glycaemic profiles and support personalised clinical care to improve diabetes management among adults with T2D in primary care. 

Check out our other blogs on hypoglycaemia, type 2 diabetes and technology.

Reference: Furler J, O’Neal D, Speight S, Blackberry I, Manski-Nankervis J-A, Thuraisingam S, de La Rue K, Ginnivan L, Doyle R, Holmes-Truscott E, Khunti K, Dalziel K, Chiang J, Audehm R, Kennedy M, Clark M, Jenkins A, Lake AJ, Januszewski AS, Catchpool M, Liew D, Clarke P, Best J, Use of professional-mode flash glucose monitoring, at 3-month intervals, in adults with type 2  diabetes in general practice (GP-OSMOTIC): a pragmatic, open-label, 12-month, randomised controlled trial. Lancet Diabetes & Endocrinology, 2020; 8:17-26.

Photo credit: “Abbott FreeStyle Libre 2 flash-glucose sensor” by Daniel Aleksanderson, licensed under CC BY-NC 2.0

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