Get the Complete Picture by Using CGM for Those With Diabetes

Eugene E. Wright, Jr, MD; Mark Harmel, MPH, CDCES


August 11, 2022

This transcript has been edited for clarity.

Hello. Let's talk about the use of continuous glucose monitoring, or CGM, in primary care. In primary care and particularly in the management of our patients with diabetes, we're typically looking at logbooks. Logbooks can have great data, but we've learned that those data aren't always accurate or reflective of all that's going on with the patient.

We also have the A1c, which is a great measure that's been around for some 30 years now. It's well validated in studies to correlate with complications and many other things. We know that A1c represents a mean average glucose over a period of time between 8 and 12 weeks. We also know that there are a number of things that can affect that average, including chronic kidney disease, blood loss, anemia, and hemoglobinopathies.

Even with that average, we can see that A1c represents blood sugar that is constantly flowing between a very narrow range or that average can be peaks and troughs through that same period of time. There is a clear need for a measurement beyond A1c to give us a better idea of what's going on with our patients.

This is where I think CGM has the real advantage. If we were to think of comparing the CGM tracings that we can get to spot blood sugars, which represent blood sugars at a point in time, that's like taking a photo. If we look at the CGM, it's representing a complete movie. Would you rather try to figure out what's going on with the story by looking at a few photos through the story or seeing the whole story? That's how I see CGM. It's providing additional information about these patients and aggregating a large amount of data, summarizing them, and organizing them into actionable information.

I can share a case that might help you understand why I think this works. We had a 75-year-old lady who came in who was on a low dose of a sulfonylurea over time. She had complained of a few episodes of "the spells," but it was notable that her A1c was at 7%. Many would think that would be good, and we'd send her out on her same medication and look for another reason for her spells.

We decided to put a CGM on her and we found that she was one of these people with large fluctuations. Despite her A1c of 7%, she was spending 30% of her time hypoglycemic, with blood sugars < 70 mg/dL, and most of that was overnight when she was completely unaware. That overnight hypoglycemia put her at increased risk for cardiovascular events.

I hope that this brief case shows you that the value of the CGM beyond A1c helps to put that A1c in the context of, "How did you get there?" It has been said that if the A1c is your destination, the CGM can show you how to get there.

Access to CGM is not uniform, but you can check your specific carriers for how access works for you. There are two basic forms of CGM. There's the professional use, where you own the equipment, you place it on the patient, you send them out, they come back, you scan, and you get a report from that. It's very similar to a Holter monitor if you've used that before.

The other form is called a personal CGM device where the patient owns the sensor and the device. They have a reader that comes with it, and many of them now have an app for their phone. They can generate the reports. They have an option to upload those reports to you through the cloud or they can bring their device into your office practice and you can download it.

Either way that you do this, the generated report is called an ambulatory glucose profile, or an AGP. I like to think of it as the EKG of glucose. The report summarizes up to 14 days of data into one tracing as if it occurred in 1 day. It shows you the highs and lows and gives you a detailed report of what the averages are, but it allows you to see things that you might not pick up on the spot glucose checks that you get with finger sticks. It certainly allows you to see things that you could never see with an A1c.

I really hope that you will consider using CGM in your practice. There are a number of tools and resources available to help you work it into your specific workflow. The American Academy of Family Physicians has a program for CME credit that you can access on their website about how to incorporate CGM into your practice. Additionally, there are other resources through the manufacturers, on the web, and through the American Diabetes Association on how to get started with CGM.

I hope that you will consider this in your practice to help you take better care of your patients living with diabetes.

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