Technological Advances in Continuous Glucose Monitoring
By Amy B. Criego, MD, MS, Medical Director, The International Diabetes Center And Anders L. Carlson, MD, Medical Director, The International Diabetes Center
Amy B. Criego, MD, MS, Medical Director, The International Diabetes Center
For people living with diabetes, managing glucose variability requires constant attention. The goal is to minimize extreme low and extreme high glucose levels. But for many patients, achieving a healthy glucose range—what endocrinologists refer to as “time in range”—can be time consuming and frustrating. People with type 1 diabetes (T1D) have to make numerous decisions each day whether to use insulin and, if so, how much to use. These dosing decisions are critical. If insulin is administered at the wrong dose, there can be dire consequences. For these reasons, advancements in diabetes technology are focused on decreasing the burden associated with glucose monitoring as well as automated insulin delivery.
Continuous Glucose Monitoring
One of the most important advances in technology is the use of continuous glucose monitoring (CGM). CGM uses a very small sensor that is worn just under the skin, with a transmitter that is attached on top of the skin. The transmitter then sends glucose data every five to 15 minutes to a receiver device, which in many cases can be a smartphone app. With the ability to get up to 288 blood glucose readings per day, compared to an average of four to six fingersticks per day using previous technologies, the amount of data and opportunity to respond to it is massive. With CGM, it is like watching a movie about a patient’s glucose levels, instead of viewing a one-time snapshot. Several CGM systems can even be shared with family or friends. This has been a major advancement for parents of children with T1D, with the peace of mind knowing they can remotely follow their child’s glucose levels.
Although it has been in clinical use for nearly 20 years, only recently have CGM devices been accurate enough to drive automated insulin delivery. There are now several on the market, they require few or no finger stick blood glucose checks, and can be reimbursed for use in broader diabetes populations. We have both “professional” and “personal” CGMs, meaning either the clinic or patient owns the device, respectively. The most common personal CGMs available in the US are made by Medtronic, Dexcom, Abbott and Sensionics. Most systems are able to alert patients to impending low or high glucose levels so they can take corrective action and improve their time in range. Each CGM differs in cost, user interface, and how they are placed on the body. But, altogether, these devices are changingthe current way we acquire and respond to glucose data.
Automated Insulin Delivery
According to data from the T1D Exchange Clinic Registry, which consists of 77 clinics in 35 states collecting common data on children and adults with T1D, approximately 60 percent of people with T1D use insulin pump therapy. The pediatric and adult research teams at the International Diabetes Center (IDC), part of the Minneapolis-based Health Partners Institute, were involved in a pivotal trial of the Medtronic 670G Hybrid Closed Loop system, the first hybrid closed loop pump system available to people living with T1D.
Anders L. Carlson, MD, Medical Director, The International Diabetes Center
The trial results were published in JAMA online September 2016 (Bergenstal et al), paving the way for approval that same month from the U.S. Food and Drug Administration. The 670G system is currently approved for people age 7 years and older. There are currently over 100,000 active users of the 670G system and the IDC is now part of a follow up study. The system incorporates a CGM sensor that attaches to the body under the skin and an insulin infusion site catheter under the skin that is attached via tubing to the insulin pump. The insulin pump uses an algorithm based on glucose data to automate insulin delivery. While users of the device still need to manually enter information into the pump before eating to ensure proper insulin dosing, the device automatically makes changes to insulin delivery between meals and overnight. When the 670G is operating in “auto mode,” the sensor glucose is updated every five minutes and insulin adjustments are made to target a glucose level of 120 mg/ dL. If the sensor glucose is trending high, the system may deliver more insulin to limit time above range. If the sensor glucose is trending low, the algorithm will reduce or stop insulin delivery to limit or even prevent time below range. Calibration of the sensor used with this device is required using finger-stick glucose values at a minimum every 12 hours.
Proper management of diabetes and devices requires that clinicians review glucose data in a standardized format. At the IDC, we’ve developed a standard one page report called Ambulatory Glucose Profile (AGP) to help clinicians review their patients’ data. Akin to the role of electrocardiography in heart care, the AGP report includes summary statistics with a glucose profile graph. The AGP allows clinicians to quickly identify opportunities for therapeutic changes, creating more time for shared decision-making among clinician and patient. The AGP was suggested as a standardized report in 2008 and in September 2018 the diabetes care community recognized a glycemic management indicator in the AGP. It’s currently licensed by Abbott, Disasend, Glooko, DexCom, Medtronic, Eversense and Sinovao.
More sophisticated medical devices and algorithms will continue to improve patients’ time in range. In addition to delivering insulin, newer devices may also administer glucagon to prevent glucose levels from going too low.
Cost and insurance reimbursement will be factors in how widely and quickly these technologies can be used. But in the meantime, the IDC remains excited to work with volunteer research participants, research collaborators and industry partners to continue easing the burden and improving care for people living with diabetes.