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The Latest in Continuous Glucose Monitoring Technology

Grazia Aleppo, MD discusses the latest in continuous glucose monitoring technology. She shares why a new name for eA1C was needed, why GMI was selected as the new name, how GMI is calculated, and how to understand and explain GMI if one chooses to use it as a tool in diabetes education or management.
The Latest in Continuous Glucose Monitoring Technology
Grazia Aleppo, MD
Grazia Aleppo, MD, FACE, FACP is a Professor of Medicine, the Director, Northwestern Medicine Diabetes Training and Education Program, and Associate Chief for Clinical Affairs for the Division of Endocrinology, Metabolism and Molecular Medicine at Feinberg School of Medicine, Northwestern University. Her primary clinical interest is Diabetes, especially Diabetes and Technology and the application of the use of Insulin pump Therapy and real Time Continuous glucose monitoring sensor therapy to Diabetes type 1 and Diabetes type 2.

Melanie Cole (Host): Today we’re examining the new glucose management indicator and the latest glucose technology. My guest is Dr. Grazia Aleppo. She’s a professor of medicine and the Director of Northwestern Diabetes Training and Education Program. Dr. Aleppo, tell us a little bit about yourself please and how you came to Northwestern Medicine.

Dr. Grazia Aleppo (Guest): First of all good morning and thank you for having me over today. So I have been at Northwestern Medicine for about 12 years and I came to Northwestern from a different institution trying to – my purpose of coming to Northwestern was to establish a diabetes program and try to apply the latest and greatest advances in diabetes technology to educate my patients and keep them the most updated tools available for their care.

Host: Tell us a little bit about the current glucose management indicator for diabetes, glucose monitoring, glucose technology, define some of the terms that you use for us on a daily basis.

Dr. Aleppo: Well glucose management indicator is the latest and newest definition of glucose levels. In fact, I’m very impressed that you’re asking the question because it’s really so new so many people don’t know about it yet so I’m happy to talk about it right now. So the GMI or glucose management indicator is the tool or a number that we obtain from two weeks at least of continuous glucose monitoring levels and we determine the number to be the estimated level of glucose status of a patient. So in the past people were thinking in terms of hemoglobin A1c which is the standard of glucose control, glucose status in modern medicine for diabetes. However, hemoglobin A1c is population based tool and even those the numbers can tell you whether there is a problem, for example, if it’s elevated, you assume there is a significant amount of hyperglycemia. It does not tell you where the hyperglycemia is or how much hypoglycemia, so low glucose versus high glucose could be behind that number. So the continuous glucose monitoring technology has been coming to us in the last 10 years, to actually almost 20 years now, to really help our patients to see what is behind the A1c. So this number was made to represent what was called in the past an estimation of the hemoglobin A1c, but the name was changed because estimation was causing confusion and it’s not really a hemoglobin A1c; it’s truly the number that is inserted in a formula and tells you what is the personal patient level of glucose indicator. We didn’t want to use the word control because control can be interpreted as a way to sort of a judgey way to talk with the patient, sort of belittling them because they could be in control or out of control, whereas an indicator shows just that indicates where a person is at and you can make interventions to do better or just leave it as it is. So why is it better than glucose monitoring? So glucose monitoring by fingerstick, traditional self management glucose monitoring unfortunately has limitations. It will tell you a point in time of a glucose level, but it doesn’t tell you where the glucose level is coming from, whether it’s going to be stable, going up or down, nor how much it’s going to fluctuate from before a meal for example to after a meal, and so our body is dynamic, it doesn’t stay still, and so do the glucose levels. So it has been giving patients information, but it’s like watching a movie with your eyes closed and opening them four times in two hours; you don’t really know what the movie’s all about, and that’s where CGM actually makes you open the eyes and see the entire movie and enjoy the whole store, and that’s where CGM comes in. It gives you information over 24 hours of the glucose levels that were now in real time, what they were and up to – you can see trend arrows that show you where the glucose are going towards in the next 45 minutes to an hour, and so here it opens a complete different spectrum of information to patients. They say, oh yes my glucose is 194 for example, but I’m going down so I’m okay. I took my insulin, I’m going to be okay, but if it’s 120 and it’s going down very rapidly with a series of arrows, I better take something to eat now. Whereas in the past you would have 120 and thought I’m perfect, without knowing that in fact the glucose was going down and so the patient should do an intervention before they have a hypoglycemic episode that could be really dangerous to their health. That makes sense to you?

Host: Well it certainly does, and as you’ve said, because the results were population based, we get that, but recently the US Food and Drug Administration determined that it was the nomenclature of the estimated A1c that needed to change, why was the name what needed to change?

Dr. Aleppo: Because the issue is that when you look at the hemoglobin A1c, the CGM values can vary, let’s say A1c of 7%, which is a glucose average of 154. The problem is that with CGM, the glucose can go between 150 and 200 and still have an A1c of 7%. For the patient it has a very different meaning, having a glucose of 150 versus a glucose of 218. So the estimation was making the FDA concerned because it was not really a blood measurement, it was a determination of an indirect information from the CGM data. Now it is important to know that two weeks, 10-14 days of CGM data provides a very good estimate of CGM metrics for about three months, which is why we’re using this system now to look at the previous, let’s say two weeks of data, as long as they are at least 70% of data within the CGM data. Now the important thing is, when you try to replace the estimated A1c because people can confuse the two, you need to give it a different name that is still telling you how am I doing in terms of is my glucose level going towards the right direction? Do I have any challenges? And so the A1c again doesn’t take into consideration patient can have anemia, patient can have a different ethnicity, or other things that can really cause a different level of A1c with the same glucose level, and it’s very important because again many factors effect A1c, but the GMI, glucose management indicator, again a way for the patient to know what is my status. I call it status because I don’t want to call it control because control is not really a pleasing word anymore. So if you think about how am I doing as a patient, the doctor is managing a patient, the patient is trying to think about how they are doing, and the result of this is a glucose management indication. So indicator in this case to really help them to understand, what am I? What is my level of status? Am I supposed to be better than that? Worse than that? Am I going too low? Am I going too high? And one number will help them, and the beauty of this is that this is a personal value. It’s not population based, it’s only person based.

Host: It makes so much sense, and when you explain it it’s so very clear and easy to understand. Dr. Aleppo, you recently published work in the journal of diabetes care on the new term for glucose monitoring. Tell us about your research and what it sought to uncover.

Dr. Aleppo: So I spent my time within my patient care and some clinical research and my purpose of doing clinical research is to work on technology such as continuous glucose monitoring, which I think may be the most important discovery or advance in diabetes in the last 50 years. Why is that? Because again when I work on research, I’m trying to make some discoveries or implementation or advances for patients who have diabetes today. Everybody sometimes is too hung up on the idea of a cure. I need to think about the patients who have diabetes today. They have to be taken care of today, so when there is, or if there is a cure for even type 1 let’s say, they are healthy enough to take advantage of it. So for me, when I work on technology, I’m trying to apply whatever has been discovered by medical engineers to my patient’s lives and they can have much more peace of mind, they can go to bed without being afraid of having hypoglycemia at night, they can go exercise, they can have fun, they can travel because they have technology that alerts and allows them to say, I think I may have low blood glucose. Is it really true? The machine is beeping. It’s 75 and you’re going down really fast, so okay better stop now and take some glucose or my glucose is going up so fast. Okay, maybe I forgot to take my insulin. And so when the patient is enabled to do it by themselves without intervention with the physician or the healthcare provider, that is a huge, huge advantage. So that’s what I do in my research. My plan is to do things that can help my patient to live a healthy with diabetes and be successful in whatever they want to do.

Host: I think one of the most important aspects of this change is the smooth transition from the old estimated A1c to this new GMI. Tell us how you would like other providers to understand and explain it to their patients if they choose to use it as a tool in diabetes education or management?

Dr. Aleppo: First of all, they have to have access to the patient’s continuous glucose monitoring data. This is not very difficult to do. Many patients have their data on cloud and so by using their phones or their readers, they can actually see usually with their phones, even with the insulin pumps, but mostly with their phones via smart apps, they can see their glucose levels at any given time through CGM and that goes to an application where you can actually – they’ll load the information during the visit and see the estimated – the GMI excuse me. Now they can either do that or they can take the average of 2 weeks of CGM data and insert it into a formula that is available online for free, and once they see the number and they compare to the patient’s hemoglobin A1c checked the same day, usually by a fingerstick or through a laboratory value, they can teach the patients based on the difference of the levels. Your A1c population base tells you that. Your GMI tells you maybe you are having more low glucose, and you, for example, some patients who are African American, they tend to have higher hemoglobin A1c with the same glucose level or very close that with a Caucasian person, so in many situation the A1c higher than the GMI, and that is because, for example, the hemoglobin A1c of a person who is African American is usually higher than a Caucasian person with the same glucose level. So there are many reasons behind that are very complicated to go through, but suffice to say that when this person comes to us and sees the GMI that is a reassurance that the glucose levels are not so high, whereas if you just look at the A1c, you will make interventions that may be aggressively or excessively aggressive and they’ll lower the glucose level of the person too much. So when we look at the GMI, we will look also at the overall data and we say, okay the GMI is a number but what is behind the number an we look at the CGM data, and we discover that a particular part of the day with increase in hypoglycemia or increase in hyperglycemia, once we address those specific areas to improve the overall percentage of glucose levels in a specific range that we call time and range. Why is that so important? Because more and more evidence from research is showing that keeping the glucose stable throughout the day with a significant percentage of glucose in time and range such as 70 to 180 mg/dL really correlated to decrease in potential for eye disease or neuropathy, whereas keeping the glucose in a very fluctuating situation with a very small time spent in range that I was mentioning before, can put the patient at increased risk for diabetes complication. This data is very new, but they are coming out in greater number, more and more. We are going to be paying attention to this. So we do that just focused on the A1c and keep it as low as possible where there could be a lot of hypo and hyperglycemia fluctuation, but rather focus on the CGM data – this shows that throughout the 24 hours where there are difficult spots with fluctuations or very safe spots with very stable glucose towards the most stable glucose of the day and the GMI helps us understand what is the specific person’s difference between the A1c and CMG reading data.

Host: As we wrap up, what great information, Dr. Aleppo. What would you like providers to know to take forward to help their patients on how to interpret GMI and use it most effectively in their clinical practice?

Dr. Aleppo: They should be aware that the patients have access to CGM. They should understand how GMI is calculated, but if I could be even one step even further, I would like them to focus not just on the GMI, it becomes again one number. They want to focus on the data that generates the GMI, and therefore understand how the GMI represents the evolution of these glucose levels throughout the latest 2 weeks or a month and see whether they need to make interventions. So I would say more awareness to CGM because it’s available for many patients for type 1 or type 2 or multiple daily injections available over the insulin pump, but also understand that a number is always going to be a number, so we shouldn’t treat GMI just like A1c. We should see what is beyond GMI. What is the data showing us and our patients and then make interventions.

Host: Tremendous information. Really excellently explained. Thank you Dr. Aleppo for your energy and your passion. I can hear that coming through. Thank you for joining us today. This is Better Edge, a Northwestern Medicine Podcast for physicians. For more information on the latest advances in medicine, please visit, that’s This is Melanie Cole, thanks so much for tuning in.