Today I am going to talk about continuous glucose monitoring (CGM). This is a topic I have addressed in the past, but it is a rapidly evolving field and I believe it is important that you understand how CGM is used in diabetes management.
The incredibly good news is that Medicare has finally approved reimbursement for CGM for seniors. This has been a battle we have been fighting and advocating for a long time, because until now, when my patients reached the age of 65, they suddenly had to give up their CGMs. This seemed incredibly bad for the patient, because it is our older patients who have more episodes of hypoglycemia. CGM is a great tool for patients because they can monitor for impending episodes of hypoglycemia and do something to prevent them.
The approval that Medicare has given is for CGM systems that are in essence strip replacement. To gain Medicare approval, the US Food and Drug Administration (FDA) had to give the device an indication as a replacement for fingerstick testing. The only device currently FDA-approved for this indication is the Dexcom G5® system.
Fingerstick replacement means that patients do not have to prick their fingers to get a blood glucose value every time they dose insulin. With this device, a patient can look at the glucose value from the CGM and use this value to calculate the insulin dose.
The Dexcom G5 does require two calibrations each day, every 12 hours. Thus, patients must stick their fingers so they can measure their blood sugar levels for these calibrations. It is very important that patients calibrate this device twice a day. But other than those two calibrations, or if they think something is really off about the sensor reading, the patients can just use the sensor for adjusting their insulin doses.
The caveat to this is that during the first 12 hours after a new sensor has been placed, the sensor may not be quite as accurate as it is subsequently. During the first 12 hours of any new sensor, I encourage people to use fingersticks if they have any doubt about their blood sugar readings. Medicare will reimburse for this, for patients with either type 1 or type 2 diabetes who are on multiple daily insulin injections or an insulin pump.
Real-Time Glucose Readings
To refresh your memory, the Dexcom G5 CGM is a device that consists of a sensor and a receiver that patients themselves can insert in a convenient place on their bodies. It may be the abdomen, the arm, or the hip. They insert a new device once a week. There is a little device that inserts it under the skin.
After a 2-hour warm-up period, the patient then receives blood glucose values that stream to their iPhones or into a receiver. The patient can set alarms and alerts for rising and falling blood glucose levels. Patients see, in real time, what their blood sugars are and can make insulin dose adjustments based on those glucose values.
That is considered real-time CGM and is something the patients can manage at home. Every week, they insert their own sensors, look at the data, and make insulin dose adjustments on an hour-by-hour, day-by-day basis. When they come in to your office, you can download the data from a given period of time—I usually look at 2 weeks' worth of data—and use this to make retrospective analyses.
You can look for periods of hypoglycemia, particularly at night. That is the first thing I look at, to try to reduce episodes of low blood sugars, particularly overnight. I look at the daytime values, the mealtime dosing, and the postprandial glycemic excursions.
I find it incredibly useful for helping my patients manage their diabetes. I use it in patients with type 1 and type 2 diabetes who are on insulin, to help them adjust their insulin doses and achieve and maintain normal blood glucose levels.
Professional Retrospective Glucose Monitoring
Another sort of CGM is the "professional" version. With this type of CGM, the patient does not see blood glucose values in real time. We place the CGM on the patient in the office, send them home, and then have them come back a week or two later when we download and analyze the data. All of that analysis is retrospective.
The newest professional device on the US market is the Libre. This is a very simple device and requires no calibration. It comes in a box that contains the sensor and the inserter device. You or your assistant can put it on the patient and then send the patient home. The patient can remove the little device and mail it back to you and you can read it, or the patient can return to the office and you can read it.
You need another apparatus—the reader—which is also used to start the device to make sure it is working. When patients return or send the device to you, you read it with another apparatus; you also can print out the past 2 weeks of blood sugar levels.
In the video, I will show you what this device looks like as it is inserted. I am the model patient today, and I have an assistant who will show how the device is inserted. He is cleaning off an area on the back of my arm; he is loading the device into the spring-loaded inserter; he is inserting it into my arm.
The inserter was placed against my skin, and a tiny needle went under my skin and then quickly retracted, which leaves the sensor under my skin. It did not hurt. This patch is now on my arm and will stay there for 2 weeks.
I have worn one of these devices, to understand what it is like and to see my own blood sugar levels. The biggest problem I had is that the device is so unnoticeable and doesn't need calibration or anything, that when I was taking a shower, I would come close to washing it off.
That is the Libre device. Once inserted, the reader clicks "on" and the monitor says it is under the skin and ready to read. This is how we do a form of professional glucose monitoring.
Again, the glucose levels are blinded to the patient and this particular device does not require any calibration. The patient just goes out, lives their life, returns to your office, and you look at the data. I really like this for my patients with type 2 diabetes when I am trying to figure out whether they are having postprandial glycemic excursions, and for some of my patients with type 1 diabetes who avoid fingersticking when they can and do not want to wear a real-time sensor.
I believe that this device can play several roles for some of my patients. My goal, however, is to have most patients wear real-time monitors so that they can make insulin dose adjustments, or exercise or make fluid intake changes based on real-time data.
But I have also found the professional CGM to be very helpful. Again, it is left on for 2 weeks. The patient can come in and have it inserted 2 weeks in advance of an appointment, so you are ready with the data when you see the patient. Or, you can insert the device at the appointment and then the patient can mail the little sensor back to you in an envelope. You can read the data from that.
Data Worth Viewing
In conclusion, I believe that continuous glucose sensing is here to stay. I know it can be a problem to look at all of the data our patients bring to us to interpret. But I believe that CGM is a tool that empowers our patients.
It lets them see their trends. It is not just some magical thing that is happening to their bodies. It shows them both real-time data, so they can see in the moment what is happening to their sugars, and retrospective data, so they can see that perhaps their nights are not so dangerous and they do not have to worry. Or they can see that chocolate cake really did do what you said and increased their blood sugar levels after they ate it.
I have only talked about two devices. I talked about the Dexcom G5, because that is now covered by Medicare. And I talked about the Libre, because that is new on the market and it has a professional version that will give you 2 weeks of blinded data for analysis. There are other sensors, in particular the Medtronic sensors that work with their insulin pumps. We have discussed those in other videos, talking about how CGM is integrated into the design of the pumps so that the pumps themselves can dose insulin off those sensors.
This is an exciting field. I know it can be overwhelming, but I believe that the data are worth looking at, and it is worth allowing your patients the opportunity to control their diabetes ever better, particularly when it comes to patients who are using insulin but are often guessing about the dose. It can be quite frightening for patients to wonder whether they are giving the right dose or the wrong dose.
Medscape Diabetes © 2017 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Two 'Incredibly Useful' Tools for Managing Diabetes - Medscape - Sep 07, 2017.
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