A new technology may help patients and caretakers better manage diabetes
Ah, the fingerstick. People with diabetes know it well. One fingerstick and a blood glucose meter, and they know their blood glucose concentrations, at least at that moment in time, and whether they need to address it, e.g., with sugar or insulin.
But fingersticks hurt. They take time. They’re a little cumbersome. And really, how many times a day is a person with type 1 or type 2 diabetes going to stick his or her finger? And what about nighttime – probably the scariest time of day for people with diabetes?
Well, the fingerstick may never go away entirely. But it may have to take its place next to a newer technology: continuous glucose monitoring.
What it is
Continuous glucose monitoring automatically tracks blood glucose levels – also called blood sugar – throughout the day and night. Since March 2018, the U.S. Food and Drug Administration has approved at least three CGM systems for marketing in the United States.
Most people who use CGMs have type 1 diabetes, though use of CGMs by people with type 2 diabetes is expected to grow, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health.
Traditional blood glucose meters allow the person to see his or her level at a glance. They can also trend their glucose concentrations over a few hours or days. But seeing continual glucose levels throughout the day with a CGM can help people make more informed, timely decisions about how to balance their food, physical activity and medicines, according to NIDDK.
A CGM works through a tiny sensor inserted under the skin, usually on the belly or arm. The sensor measures interstitial glucose level, which is the glucose found in the fluid between the cells. The sensor tests glucose every few minutes. A transmitter wirelessly sends the information to a monitor. The monitor may be part of an insulin pump or a separate device, which might be carried in a pocket or purse. Some CGMs send information directly to a smartphone or tablet. So, if you’re talking about a child with diabetes, his or her parents can view what’s going on at all times and advise the child on what to do next.
280 readings a day
Blood glucose testing is the common way to test response to therapy, whether to intensify or de-intensify treatment, and to avoid the risk of low blood sugar, says Guillermo Umpierrez, M.D., CDE, chair of the American Association of Clinical Endocrinologists’ Diabetes Disease State Network, and professor of medicine, Emory University. People with type 1 diabetes may need to test as frequently as four to eight times daily; those with type 2 who take insulin perhaps two to four times; and those with type 2 who do not take insulin, perhaps one to two times per week.
While very effective, blood glucose testing can be expensive, with the cost of the strips representing a significant cost to the overall care of the patient, he says. “But perhaps its biggest shortcoming is that glucose meters tell you how your blood sugar is doing at the time of testing, which may not represent the average glucose concentration during the day.
CGM has been shown in clinical studies to be a better way of controlling diabetes in patients with type 1 and type 2 diabetes than point-of-care testing, says Umpierrez. It can significantly reduce the risk of hypoglycemia and may decrease the risk of diabetic emergencies.
“Most of these devices check blood glucose every 5 to 15 minutes, so you have about 280 blood sugar readings a day, instead of just a few times per day,” he says. “Because of that, the CGM devices are able to provide a better glucose assessment throughout the day.”
Some CGM systems have alarms, which sound when blood glucose is too low or too high. “For those treated with insulin, our main concern is hypoglycemia,” he says. “Because the devices show trends, CGMs can alert the patient even before hypoglycemia occurs.
“The hazards of hypoglycemia at night are recognized; but nocturnal hypoglycemia is less recognized during the day, because the body doesn’t respond the same at night as during the day. Alarms are very, very helpful, not only for patients, but for caretakers, spouses or parents.”
Some CGMs – referred to as professional CGMs – are sold directly to physicians. The patient wears one for 10-14 days, then brings it back to the office for review by the physician. The other type of CGM is the personal CGM, which patients own and with which they conduct their own monitoring. (They may share data with their physician via a Bluetooth connection.)
“The other area where our group is investigating CGMs is in the hospital,” says Umpierrez. In the hospital, most patients with diabetes are being treated with insulin, so hypoglycemia is common. Testing with CGM in the hospital can help improve the overall care of diabetes.
The downside of CGM systems? They are expensive, and, while frequently covered by insurance for people with type 1 diabetes and insulin pumps, not so much for those with type 2, he says.
“Also, there is a lack of education on continuous glucose monitoring and its benefits,” he adds. “Unfortunately, primary care providers have not used CGM as frequently as they should. In fact, fewer than 20 percent of primary care providers are familiar with it. So we still have a lot of education to do.”
Peace of mind
CGMs can help a lot of people who have a hard time keeping their glucose levels in a safe range, says Matt Petersen, vice president of medical information, American Diabetes Association. That’s particularly true for those who take insulin.
“Early on, people with diabetes generally have a fairly good sense of when their blood glucose is too low,” he says. “They may become sweaty, ill-tempered, confused. And they recognize these symptoms for what they are – low blood glucose. So they’ll do a check and see if they need to have something with sugar to raise blood glucose levels back up.
“But that ability to detect approaching hypoglycemia tends to diminish over time. It’s called hypoglycemia unawareness. And it’s a problem, because you may think you’re doing fine, but you’re actually in a dangerous situation. Continuous glucose monitors can help with that.”
The need for CGM is less obvious for people who are managing their type 2 diabetes with oral medications rather than insulin, he continues. That’s because they rarely experience the acute changes in blood glucose levels as those taking insulin.
Many people with diabetes consider the most valuable asset of CGMs to be the alarms that alert them when their glucose levels are trending downward, says Petersen. That’s a bonus during the day. “If I’m in a meeting or something, I don’t have to be thinking about my blood glucose level all the time,” he says. And it’s especially reassuring at night, when people with diabetes can’t check their glucose levels with regularity. In short, CGMs can give people with diabetes some guidance and peace of mind.
The ADA encourages primary care physicians to get the education they need in order to work with their patients on using continuous glucose monitors, says Petersen.
“We know of many primary care providers who want CGMs to be more widely used,” he says. “As CGMs become easier to use, which is happening, providers will feel more comfortable prescribing their patients to use them.”
HbA1c testing: A must
Even as continuous glucose monitoring systems gain in popularity, the need for HbA1c testing remains strong, says Guillermo Umpierrez, M.D., CDE, chair of the American Association of Clinical Endocrinologists’ Diabetes Disease State Network, and professor of medicine, Emory University. That’s because continuous glucose monitoring shows blood glucose levels on a daily basis, whereas HbA1c looks at average blood glucose control over the past 90 to 120 days.
The American Diabetes Association puts it this way: “In some ways, the A1C test is like a baseball player’s season batting average; it tells you about a person’s overall success. Neither a single day’s blood test results nor a single game’s batting record gives the same big picture.”
“HbA1c is the best tool we have to measure the effects of therapy,” says Umpierrez. Patients with high HbA1c levels are at increased risk of retinopathy, kidney disease and neuropathy, he adds.
CGM: The players
Most oft-mentioned players in the continuous glucose monitoring market:
- Dexcom Inc. (San Diego, California). The Dexcom G6® CGM System was cleared for marketing by the FDA in March 2018 for use as both a standalone CGM and for integration into automated insulin dosing systems. The system eliminates the need for fingersticks for calibration or diabetes treatment decisions. In June 2018, Dexcom announced that the U.S. Centers for Medicare & Medicaid Services updated its policy on mobile device compatibility for the Dexcom G5® CGM System, making it the first mobile-enabled CGM system for Medicare patients with diabetes that works to display and share real-time glucose activity.
- Abbott (Abbott Park, Illinois). The Abbott FreeStyle® Libre system is a continuous glucose monitoring system consisting of a handheld reader and a sensor worn on the back of the upper arm. The FreeStyle Libre Flash Glucose Monitoring was approved for marketing by the FDA in September 2017, and was the first CGM system that could be used by adult patients to make diabetes treatment decisions without calibration using a blood sample from the fingertip. (That said, fingersticks are required for treatment decisions when the person sees the “Check Blood Glucose” symbol, when symptoms do not match system readings, when readings are suspected to be inaccurate, or when the person experiences symptoms that may be due to high or low blood glucose.)
- Medtronic (Dublin, Ireland). The Guardian™ Connect was approved for marketing by the FDA in March 2018 for people with diabetes ages 14 to 75 years. The Guardian Sensor glucose levels are not intended to be used directly for making therapy adjustments, but rather to provide an indication of when a fingerstick may be required to measure glucose levels. All therapy adjustments should be based on measurements obtained using a home glucose monitor and not on glucose levels provided by the Guardian Sensor
- Senseonics Holdings Inc. (Germantown, Maryland). In June 2018, the Senseonics Eversense® became the first FDA-approved continuous glucose monitoring system to include a fully implantable sensor to detect glucose, which can be worn for up to 90 days. A sensor is implanted just below the patient’s skin by a physician. A fluorescent chemical coating on the outside of the sensor generates a small amount of light in response to the amount of sugar that is present in fluid under the skin (interstitial glucose). This light signal is converted into a glucose reading and transmitted wirelessly every five minutes to a compatible mobile device.
What is an artificial pancreas?
The “artificial pancreas” you may be hearing about is not necessarily what you think. It does NOT involve biomaterial, synthetic or artificial tissue or organs. But it does replace reliance on 1) fingerstick testing or 2) continuous glucose monitoring systems and 3) separate, non-integrated delivery of insulin by shots or pump.
An artificial pancreas monitors blood glucose levels around the clock (continuous glucose monitoring), and automatically adjusts the delivery of insulin to reduce high blood glucose levels and minimize the incidence of low blood glucose. Little or no input is required from the patient. The system can be monitored remotely, for example, by parents or medical staff.
In September 2016, the U.S. Food and Drug Administration approved the first “hybrid closed-loop system” – the Medtronic MiniMed 670G System – for people with type 1 diabetes. The system tests the glucose level every 5 minutes throughout the day and night through a CGM, and automatically gives the person the right amount of basil insulin – a long-acting insulin – through a separate insulin pump. The person still needs to test his or her blood with a glucose meter a few times a day. And they will manually adjust the amount of insulin the pump delivers at mealtimes and when a correction dose is needed.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) has funded – and continues to fund – several studies on different types of artificial pancreas devices to better help people with type 1 diabetes manage their disease.