Is CGM a Tool or an Intervention?
In this podcast, Savitha Subramanian, MD, and Eugene Wright, MD, compare the roles of blood glucose monitoring (BGM) and continuous glucose monitoring (CGM) as tools and/or interventions in diabetes management and suggest that CGM can function effectively as a tool and an intervention.
Additional Resources:
- Wright EE Jr, Subramanian S. Is continuous glucose monitoring a tool, an intervention, or both? Diabetes Technol Ther. 2023;25(S3):S48-S55. doi:10.1089/dia.2023.0025
- Farmer A, Wade A, French DP, Goyder E, Kinmonth AL, Neil A. The DiGEM trial protocol--a randomised controlled trial to determine the effect on glycaemic control of different strategies of blood glucose self-monitoring in people with type 2 diabetes [ISRCTN47464659]. BMC Fam Pract. 2005;6:25. doi:10.1186/1471-2296-6-25
- Polonsky WH, Fisher L, Schikman CH, et a. Structured self-monitoring of blood glucose significantly reduces A1C levels in poorly controlled, noninsulin-treated type 2 diabetes: results from the Structured Testing Program study. Diabetes Care. 2011;34(2):262-7. doi:10.2337/dc10-1732
- Aleppo G, Beck RW, Bailey R, et al. MOBILE Study Group; Type 2 Diabetes Basal Insulin Users: The Mobile Study (MOBILE) Study Group. The effect of discontinuing continuous glucose monitoring in adults with type 2 diabetes treated with basal insulin. Diabetes Care. 2021;44(12):2729-2737. doi:10.2337/dc21-1304
- Wright EE Jr, Kerr MSD, Reyes IJ, Nabutovsky Y, Miller E. Use of flash continuous glucose monitoring is associated with A1C reduction in people with type 2 diabetes treated with basal insulin or noninsulin therapy. Diabetes Spectr. 2021;34(2):184-189. doi:10.2337/ds20-0069
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TRANSCRIPTION:
Jessica Bard: Hello everyone, and welcome to another installment of Podcast360, your go-to resource for medical education and clinical updates. I'm your moderator, Jessica Bard, with Consultant360, a multidisciplinary medical information network.
Categorizing continuous glucose monitors as a tool, an intervention, or both may appear insignificant, yet according to Dr Savitha Subramanian and Dr Eugene Wright, mislabeling CGM risks overlooking its full potential utility.
In this podcast, Dr Subramanian and Dr Wright discussed their opinion article titled "Is Continuous Glucose Monitoring a Tool, an Intervention, or Both?"
Welcome to the podcast. Please introduce yourselves to the audience.
Savitha Subramanian, MD: I'm Savitha Subramanian. I'm a professor of medicine in the division of metabolism, endocrinology, and nutrition at The University of Washington.
Gene?
Eugene Wright, MD: My name is Eugene Wright. I'm the medical director for performance improvement here at the South Piedmont Area Health Education Center in Charlotte, North Carolina and a consulting associate in the Department of Medicine at Duke University Medical Center.
Dr Subramanian: We're talking about whether a CGM is used as a tool or an intervention. So, why did we even write this opinion piece?
Dr Wright: That's a great question. And as you know, Savitha, we got into this discussion about whether CGM is a tool or an intervention. And we primarily got into that because the studies that investigate the use of diabetes technologies, such as blood glucose monitoring and continuous glucose monitoring, often report contradictory findings regarding the efficacy and in clinical utility. Whereas some of the studies of a given technology have shown no benefit, others have reported significant benefit. So, these incongruities derive from how the technology is viewed: is it viewed as a tool or an intervention?
In this article, we discussed the earlier studies that illustrate the contrasts between the use of blood glucose monitoring as a tool vs. use as an intervention and compare and contrast the roles of blood glucose monitoring and continuous glucose monitoring as tools and /or interventions in diabetes management. We suggest that CGM can function effectively as both.
Dr Subramanian: Can you describe what a tool is, Gene?
Dr Wright: For the purpose of this article, in our discussion here today, we defined a tool as a device, medication, or measure that can be used simply to accomplish a specific task.
And now, how do we define an intervention?
Dr Subramanian: I would say an intervention is an action or an approach that's initiated to treat a condition, prevent harm, and generally improve overall health. And Gene, it might seem that trying to differentiate a tool from an intervention might seem trivial, but it's important to really understand this distinction in order to be able to appropriately interpret influential research.
Dr Wright: You know, I think you're absolutely right. An intervention does imply an action with it. So what's the data on blood glucose monitoring used as a tool or an intervention?
Dr Subramanian: I'd like to highlight two studies, Gene. One is the study that came out of the UK in 2009, and that was the DiGEM or the diabetes glycemic education and monitoring study.
This was an open, randomized, three-arm parallel-group trial, which was done in primary care clinics. They recruited about 450 people with type two diabetes treated with just lifestyle intervention alone or oral agents. So, these are insulin-naive subjects, and they were divided into three arms.
One was the control arm, and the control arm did not receive any glucose monitors, they did not receive any extra instruction.
There was a second arm, which they call a less intensive self-monitoring arm, where they got glucose meters and test strips, and they were asked to test their blood sugars two days a week, three times a day and that's the less intensive monitoring arm.
The more intensive monitoring arm, they were asked to check two days a week, three times a day but they had got more test strips, and they could check as many times as they wanted. This arm also received instructions on what to do with the numbers. They got some education on exercise and lifestyle adjustments based on what their glucose monitoring results gave them.
However, this study did not really see any difference in the three arms in using no glucose monitoring with a glucose meter versus testing a few times a week or more. The subject started off with a baseline A1C in the low to mid 7% range, and it didn't change at all.
So, this study concluded that blood glucose monitoring really did not help in people with type 2 diabetes who were not on insulin, just on oral agents.
And here I want to point out, so this would be a study where they used the glucose meter primarily as a tool. And the study authors also concluded that using the blood glucose monitor in type 2 diabetes wasn't really beneficial and also added to cost of management.
But I will say this was a 2009 study, and really it was a different era, of course it's almost 15 years ago, but it was also not clear what kind of education the subjects got because the paper didn't expand on that.
That's the the DiGEM study, but then in contrast, there was the STeP study that was published in Diabetes Care in 2011 by Dr Bill Polonski's group. And here they also use a pretty similar number of patients and similar subject populations. So, there were about 480 patients with type 2 diabetes who were suboptimally managed. And the study was done out of primary care. There were about 34 primary care clinics from where patients were recruited. The baseline A1C was about 8.9% and the subjects were randomized to two groups.
One was the active control group where they got a meter, but they weren't really asked to check it any number of times. They could do whatever they wanted, however many times they wanted to check their blood glucose.
And the structured treatment arm subjects were given the glucose meter and asked to check seven times a day, for three days before research study visits.
So, they were asked to come in at one month, three, six, and nine months. The study ended at one year. And so, before each of these visits, they were asked to check at fasting, before a meal, two hours after a meal, and at bedtime, for at total of seven times. They were also asked to write it down, and so they could see the data, and they were also taught what to do with the data that they saw.
And what this study showed was, with the structured intervention, there was actually a significant decrease in A1C. The A1C dropped to 7.6 %, and so the study authors concluded that using this blood glucose monitor as an intervention where they could act on the readings was actually beneficial.
I do want to point out that because in the control group also there was a decrease in A1C from 8.8% to 7.6%, so there was a 0.8 to 0.9% drop, and that was probably because it was more intensive scrutiny of these folks and they got free meters and they got free test tips and so they had access to this. And so, indirectly they were maybe able to intervene on their readings even though they weren't given the structured education the other arm did. The STeP study actually did use the meter as an intervention tool.
So, what's the data on CGM as intervention vs tool, Gene?
Dr Wright: We looked at this in our article and in some other articles, and I see CGM in this situation as the next generation of structured testing. But with the ambulatory glucose profile, it now either facilitates or becomes an intervention.
CGM, as we know, takes a large stream of glucose data, organizes it, analyzes it, summarizes it, and then visualizes it into an ambulatory glucose profile. This process transforms data into actionable information that can be used by both the patient and the health care professional to manage glucose. So, to demonstrate this point, we looked at two studies, the MOBILE study, which was a randomized controlled trial, and another real-world observational study of a large database of poorly controlled people living with diabetes who received a CGM and a comparison of their pre-and post-acquisition glycemic control. In the MOBILE study, the key question was, for adults with poorly controlled type 2 diabetes with a mean A1c around 9%, treated with basal insulin without prandial insulin, in primary care practices, does continuous glucose monitoring improve the A1C levels compared with blood glucose meter monitoring?
Well, they found in this setting that included 175 adults with type 2 diabetes, there was significantly greater reduction in the A1C levels over an 8 month period with continuous glucose monitoring compared with blood glucose meter monitoring, about 1.1 % vs 0.6%. So, this says that continuous glucose monitoring resulted in better glycemic control compared with blood glucose meter monitoring in adults with poorly controlled type 2 diabetes, treated with basal insulin, without prandial insulin.
Now, the second study that we reviewed is a real-world database study, retrospective, observational study that used the IBM Explorers database to assess changes in A1C after a prescription for a CGM in a large population of suboptimally controlled patients with type 2 diabetes treated with non-intensive insulin therapy. Now, the inclusion criteria for this study were the diagnosis of type 2 diabetes, less than 65 years of age, treatment with basal insulin or non-insulin therapy, they had to be naive to any CGM device. And they had a baseline, A1C, of greater than or equal to 8%. And they got a prescription for a CGM during the period between October of 2017 and February of 2020.mEach patient served as their own control.
So, what do we see? Of a total, as a total of 1,034 adults with type 2 diabetes were assessed, more patients received non-insulin therapy, a little bit over twice as many than basal insulin therapy. We observed significant reductions in A1C in the full cohort from about 10.1% to 8.6%, for about a 1.5 % drop. The largest reduction we're seeing in patients who had a baseline A1C greater than or equal to 12%, and that was about 3.7%.
There were significant reductions seen in both treatment groups of basal insulin of about 1.1% but what surprised us was that the non-insulin group got a 1.6 % drop in A1C. So, we concluded from this that the prescription for the CGM in this case was associated with a significant reduction in A1c in patients with type 2 diabetes who were treated with basal insulin or non-insulin therapy.
And since that time, but not included in our study, was a more recent study that amplifies this. In this study, it’s called The Community Glucose Monitoring Project that was led by Dr Tom Grace and the health department in Findlay, Ohio.
They introduced CGM to all people who living with type 2 diabetes, regardless of insulin use. In the project, CGMs were made available to any resident with type 2 diabetes and had an A1C of greater than 7.4%.
The data was presented from the first 237 patients who had completed at least six months of the program and the mean A1C at baseline was about 9.4%. These were patients with a mean age of around 59 and a mean BMI of about 35 and a duration of diabetes of about 11 years. After six months, the mean A1C dropped from 9.4 % to 7.1%. Now, that seems impressive, but what is even more impressive is that in a primary care setting, the patients did not receive any special support or training as a part of the study. Instead, access to the CGM data alone was driving the massive improvements in the A1C. Over half of the participants, about 54%, achieved an A1C of less than 7% at six months. And about 83% got an A1C of less than 8% at six months.
So, you kind of wonder now, this is without special training on this, when we start to think about, “is it a tool or an intervention?” it is becoming increasingly clear, at least to me, that this is a tool that facilitates or actually is an intervention in and of itself.
Dr Subramanian: Absolutely, Gene. Let me ask you this: BGM or CGM?
Dr Wright: Trick question. Trick question. Well, for me, clearly, the CGM is the way to go. Some of the comments that were heard back from this study was that it makes the invisible visible. It helps people with effective decision-making. It enhances their self-efficacy. They feel more in control of their diabetes, as opposed to their diabetes controlling them. They're able to make better decisions about diet and physical activity and changes in medication. All of these things are actions that the patients take just seeing the data in a format that allows them to take action.
Dr Subramanian: So, the visibility of the data… so, we could use a blood glucose monitor and if the data is visible, instead of just sitting in there, as in the STeP study where they actually plotted out their numbers and they were able to make a change. But the CGM, the amount of data it has is so much, as you mentioned before. Visualizing it probably helps people make better decision.
And the A1C drop is significantly greater using a CGM vs a BGM. That said, with access issues, for those who want to use a blood glucose monitor, and that's all that's available, I still think there is a role because not everyone has access to a CGM. But clearly, using these tools as interventions obviously helps our patients.
Dr Wright: You know, Savitha, I think also the other part of that that we didn't talk about in our paper so much, but it's certainly a part of that, is that the patients who have some prior knowledge to interpret the information that is presented to them is important. The motivation… they need to be motivated to make the necessary changes. They have to feel that they can in fact do that. And I think the CGM actually facilitates that.
And then the external support… clearly, they need their health care team and family to be able to make these changes. All of these things are important.
What I think the difference between the BGM and the CGM is, the CGM really now presents this in a more actionable format for them.
And like the STeP study, when people could see graphic representations of their glucose data, they understood it better. The CGM, I think as I said earlier, is the next generation of that.
Dr Subramanian: Absolutely, wise words, Gene.
Dr Wright: I think this is great. I would encourage people to listen to this, to think about using CGM in their patients, and hopefully they'll get the same results.