Get the Facts on Continuous Glucose Monitoring

Until now, care for insulin-dependent diabetes has focused on the delivery of insulin combined with frequent blood glucose (BG) testing. Keeping your A1c down is, and always will be, the name of the game. But numerous studies have shown us in the last few years that having access to continuous glucose data has a huge impact. How you deliver the insulin doesn’t necessarily matter-you can use a pump, a syringe, or an insulin pen, it’s knowing your personal BG trends that makes all the difference.

So how can you get this constant feedback about your blood glucose? The answer is by using continuous glucose monitoring (CGM). CGM has been in the news a great deal in the last few years. It’s a new technology, considered still in its early stages, but the information it provides is invaluable. The devices and the necessary sensors are expensive and there has been a groundswell of online petitions, news articles (search for “CGM”), and more to get insurance companies to cover them. With last year’s JDRF study (see below), the awarding of codes that enable companies to bill for them, and new generations of the technology, CGM is clearly a welcome addition to the diabetes fight.

What is continuous glucose monitoring?
If fingersticks give you a snapshot of what your blood glucose level is, CGM is, in the words of Deborah Ruppert of Dexcom, “like looking at a movie instead of a still frame.” CGM helps you to know how to react when you’re exercising, eating, and insulin dosing. CGM teaches you your personal blood glucose (BG) trends, allowing you to more fully understand how to respond. Let’s say you’re getting ready for bed, your fingerstick tells you your blood glucose is 120. Good, you’re happy with that. But you don’t know if you’re trending up or trending down. In four hours, you could experience hyperglycemia or you might be headed for a dangerous low while you’re sleeping.

CGM helps you to understand your trends. The trends are displayed on the system’s monitor and can be downloaded into free, proprietary computer software that allows you chart your history and to share the info with your healthcare professionals over the Internet.

Any scientific evidence that CGMs are better than fingersticks alone?
The Juvenile Diabetes Research Foundation (JDRF) funded a one year study last year with 322 patients-adults and pediatric. It was the largest personal CGM study ever conducted and compared meter readings with glucose sensor readings in patients using insulin pumps or multiple daily injections. The six month study results were published in The New England Journal of Medicine (Oct 2008).  

Study Highlights:

  • More usage equals better control: higher utilization of Personal CGM is associated with greater A1C reduction
  • More patients in the Personal CGM group had A1C reductions (53% absolute reduction in adults)
  • All ages using the device at least six days a week had substantially lower A1c levels
  • Improvements in A1c occurred without the risk of hypoglycemia

The STAR 1 study got similar results after six months.  Adults wearing a glucose sensor at least six days a week experienced a 0.7% to 0.9% drop in their A1c. 

According to an article in Diabetes In Control (issue 434) the study investigators said these were important results “because the landmark Diabetes Control and Complication Trial (DCCT) found that a 10% reduction in A1c correlated with a 40% reduction in the development and progression of diabetic retinopathy.”

What are the components in a CGM device?
A CGM is made up of a monitor, a sensor, and a transmitter. It does not deliver insulin the way an insulin pump does. People who use CGM technology must have an additional device to inject insulin, whether by a pump, a syringe, an insulin pen, etc. The sensors are disposable and look a little bit like an infusion set for a pump. The transmitter fits over the sensor and is not discarded, just attached to the new sensor each time. The FDA dictates how long each company’s sensor can be worn. Currently, Dexcom’s SEVEN PLUS can be worn the longest-seven days.

[Diabetes Health has heard anecdotally that some people use the sensors for longer amounts of time than is indicated by the FDA in the same way that some people re-use lancets and other equipment meant to be disposable.]

CGMs have large, easy-to-read screens; can download trending information to computers and the internet; and boast customizable alarms that alert the user before high and low blood sugars become extreme. All three models have sensors and transmitters that can be worn in the water but the receiver (monitor) needs to stay dry.

How does a CGM work?
A small, sterile, disposable glucose-sensing device called a “sensor “is inserted into the subcutaneous tissues, using the same procedure as inserting the needle into the end of the catheter used with insulin pumps. Usually a CGM is worn on the abdomen. You wear a sensor that averages interstitial fluid (ISF) glucose levels every few minutes. This is different from a blood glucose monitor which measure blood glucose from a blood sample (fingerstick). A wireless handheld monitor shows and records the trends. The information delivered by the sensor allows you to make informed decisions about how much insulin to take. You then deliver the insulin via an insulin pump or via injections.

Is a CGM just like an artificial pancreas?
Alas, no. The artificial pancreas is not here yet. You can’t be passive with a CGM. Daily fingersticks are still required to calibrate the system and are recommended before making treatment decisions. Your brain has to process the information the device affords you. The first barrier to turning a CGM into an artificial pancreas is getting rid of the fingersticks. Nobody likes them; they hurt, they’re inconvenient and sometimes embarrassing, and the test strips are expensive. If a CGM device could test your blood, then the next step would be to have it conduct smart algorithms that could make treatment decisions. But that’s a few years off. For now, the FDA says that all treatment decisions should be confirmed with a fingerstick.

How is the data from the CGM used?
Most people find the most data in day-to-day use. They use the data “on the spot” to help spot trends and to see how quickly their glucose is rising or falling. The high and low glucose alerts can be customized to let you preemptively “head off” a high or low.  The data and trends can also be shared electronically with your healthcare professionals.

Sounds great! Why doesn’t everyone use a CGM?
People want treatment options that are convenient and affordable. Since the technology is so new and constantly changing, the devices, and especially the sensors, are expensive. Fingersticks are required twice a day to calibrate the device and the FDA recommends that fingersticks be done before making treatment decisions. Some people feel that until the fingerstick problem is taken care of, it’s not worth it. Insurance companies are coming onboard to pay for them but the cost can still be high for the user. In addition, it takes some time and training to learn how to use CGM effectively. All the CGM companies provide excellent support and training but it is a commitment, especially in the beginning.

Many people like the customizable alarms that give early warnings of hypoglycemia and hyperglycemia. Other people are irritated by the alarm sounding when they feel it’s unwarranted.

Can a person with type 2 diabetes use a CGM?
Most insurance companies require the user to be using insulin and having issues with hypoglycemia so there are only a few type 2 folks who use CGM and they are probably paying “out of pocket.”

Dexcom’s Ruppert knows of several athletes with diabetes who use the product. “They say that being able to very closely monitor their glucose significantly contributes to their performance.”

How many CGMs are on the market right now?
There are three CGMs available to the public; Medtronic’s Paradigm REAL-Time, Dexcom’s SEVEN PLUS, and Abbott’s FreeStyle Navigator System. The biggest difference between them is the proprietary technology in their sensors. They all use different technology and it’s important to understand that one model may work better for you than another model. Talk to your healthcare professional and CGM sales representatives to determine which device is the right one for you.

Paradigm REAL-Time from Medtronic
Medtronic had the first device approved by the FDA. They claim more than ten years of working with CGM technology and more than 25 years of pump technology.

Since Medtronic is also a pump company, they currently have the only system that integrates an insulin pump with continuous glucose monitoring. You can also get a stand-alone version of their CGM, the Guardian REAL-Time System, that doesn’t include the insulin pump. Steve Sabicer of Medtronic says that many of their users start out on a pump, stabilize their diabetes, and then add the CGM component after a month or so. Medtronic’s CGM is a Paradigm One Touch monitor paired with Mini Med pump.

The cost for Medtronic’s system is currently $999. if the user is already on the Paradigm pump. The entire system costs $7000. before the insurance portion. The co-pay is usually between $200 – $1000. Sabicer says that more than 50 percent of CGM sales now receive some insurance reimbursement. He says that’s up from less than 10 percent last year.
Medtronic is committed to the long-term success of CGM therapy and has invested more than $25 million in this year’s clinical strategy. They have six clinical studies underway around the world.

The Paradigm is supported by a large training staff. Medtronic has 24-hour support, online tutorials, and lots of troubleshooting tools available to the CGM user. Their
CareLink software combines device-derived data with patient self-reported treatment information into simple reports that make self-management easier. Information can also be shared with healthcare professionals in order to refine therapy and improve blood sugar control.

SEVEN PLUS from Dexcom
DexCom’s latest model is the SEVEN PLUS. The company plans to offer an upgrade to people currently using the Dexcom SEVEN. The SEVEN PLUS has easy-to-read glucose trends, customizable alerts, and a special Hypo-Safety-Alarm to help you stay in your target range.

DexCom started as an implantable sensor company ten years ago. For various reasons, their current products are external but their research in developing a sensor that would last for a long time and that would be accepted by the body helped them create the only FDA-approved sensor that can be worn for up to seven days. The SEVEN and SEVEN PLUS boast a small and flexible sensor with a round shape, designed to flex and move as the body does.

DexCom DM2 software is an accessory software program facilitating the transfer of glucose data stored by the SEVEN System into a personal computer. Once the data is downloaded, the DM2 Software displays the glucose values and calibration blood glucose values in both charts and tables to help analyze trends and patterns. The software can be used by either a clinician or an end user.

DexCom is currently offering a cash discount price for customers without insurance. The special introductory price of $799. for the SEVEN PLUS is for customers who either don’t have insurance or whose plan does not yet cover CGM. A 4-pack of sensors is listed on their website for $399.  They have a special cash discount for people who can’t bill their insurance: $275. per 4-pack.

Dexcom has plans to integrate their CGM system with other manufacturers’ pumps allowing the CGM monitor and the pump to communicate with each other.

FreeStyle Navigator system from Abbott Diabetes Care
The FreeStyle Navigator System is the latest addition to the CGM market. It features customizable early-warning alarms 10 to 30 minutes in advance to significantly reduce hypoglycemic and hyperglycemic episodes. It is the only system that offers continuous glucose readings every minute and it contains a built-in FreeStyle meter for convenient calibration (a minimum of 4 calibrations are needed over a five day period) and confirmatory blood glucose tests.

The CoPilot Health Management System for the FreeStyle Navigator system, is user-friendly and free of charge. The CoPilot system, a Windows-based PC software solution, also helps healthcare professionals manage their patients’ glycemic control.

Abbott is not a direct distributor of the FreeStyle Navigator system, but has contracted with several authorized durable medical equipment DME suppliers and. A list of current authorized DME suppliers and distributors is available through the Abbott Diabetes Care Resource Center by calling 1-877-4ADC-INFO (1-877-423-2463).

The system kit including monitor, transmitter and charger is generally priced by DME suppliers at an average price of $1450. The sensor kit containing a month’s supply of sensors (6 sensors per kit) is generally priced by the suppliers at an average price of $450. A sensor can be worn for up to five days, after which it should be replaced.

Deciding whether CGM is right for you
When it comes to diabetes management, what works for one person might not work for another. You need to take an active role in selecting which tools will help you to successfully manage your diabetes. Like many things in life, you will get out of a CGM system what you put into it. The goal with all of these devices is, as Deborah Ruppert of Dexcom says, to make diabetes a smaller part of your life so you can get on to doing what you really enjoy.

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