CGM ‘becoming standard of care’ in diabetes management, with or without insulin use
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BOSTON — Continuous glucose monitoring is a well-established therapy for type 2 diabetes on intensive and less intensive therapy, but education, training and infrastructure in the clinic are crucial to its success, according to a speaker.
“Both professional and personal CGM have roles in the management of type 2 diabetes, and both randomized controlled trials and real-world evidence support the use of CGM for the management of type 2 diabetes,” Irl B. Hirsch, MD, professor of medicine at the University of Washington School of Medicine in Seattle, told Healio. “The future for improved [CGM] technology looks bright.”
Mean absolute relative difference, the metric used to assess the accuracy of CGM, has improved greatly since the first CGMs became available about 20 years ago, Hirsch said during a presentation at the Cardiometabolic Health Congress. Today’s CGMs, whether professional or personal models, provide a much clearer glycemic picture than an HbA1c or a fingerstrick glucose reading, Hirsch said, and the changes that often result from a patient wearing one can improve diabetes outcomes.
‘Don’t always believe the HbA1c’
Data show that professional CGM in the primary care setting, with an MD or a nurse/certified diabetes care and education specialist care model, is effective at lowering HbA1c, increasing time spent in the recommended glucose range and reducing time spent in hyperglycemia, without necessarily requiring additional medications, Hirsch said.
Professional CGM, which involves a patient wearing a CGM device provided by their health care provider's clinic for up to 2 weeks, with glucose readings either blinded or unblinded for the patient, is most often used to gain a clearer picture of a patient’s glycemic profile and provide actionable data, Hirsch said. This is particularly helpful when there is discordance between a person’s HbA1c and fingerstick glucose measurements, Hirsch said.
“This happens a lot — the fingerstick says one thing and the HbA1c says something else,” Hirsch said. “HbA1c is not a perfect biomarker. It is what CMS and all of the insurance companies demand, for your patients to get an HbA1c [to get a CGM]. But I say, do not always believe the HbA1c. The CGM will teach you a lot, and it has taught me a lot over the years.”
“Dramatic impacts’ with personal CGM
More than half of Hirsch’s patients with type 2 diabetes and more than 90% of those with type 1 diabetes in his clinic are currently using a personal CGM to monitor their glucose, he said.
“One of the reasons for that is in our state [of Washington], Medicaid and Medicare approved use of these,” Hirsch said.
New advances in CGM will make the devices even more accessible for patients, he said. The new Freestyle Libre 3 (Abbott) will send readings to a smartphone every minute, has a disposable sensor and is smaller than its previous iteration, about the size of two pennies stacked on top of each other. It has a longer range than the previous Libre sensor (33 feet vs. 20 feet), and allows for direct upload to the cloud with the LibreLink app.
The Dexcom G6 is also FDA-approved for non-adjunctive use and is an integrative CGM, or i-CGM, meaning it can be paired with smartpens and other devices. It has a 10-day sensor and sharing features, allowing family members to monitor children or older adults with diabetes.
Both the American Diabetes Association (ADA) and the American Association of Clinical Endocrinology (AACE) recently updated their Standards of Care and 2021 Clinical Practice Guidelines, respectively, to include recommendations for CGM use in type 2 diabetes. The ADA states the real-time or intermittently scanned CGM should be offered for diabetes management in adults with diabetes on multiple daily injections or insulin pump therapy who are capable of using devices safely and can be used for diabetes management in adults with diabetes taking basal insulin. AACE similarly states that CGM “may be recommended” for adults with type 2 diabetes who are treated with less intensive insulin therapy.
“Anyone [taking] insulin should be on CGM; even if not on insulin,” Hirsch said. “In fact, I will say that, anecdotally, CGM can have dramatic impacts even for people with prediabetes. CGM is becoming a standard of care as a way to monitor glucose.”
‘Keys to success’ with CGM
It is important to keep in mind several important “keys to success” for successful CGM use, Hirsch said. The most important is education and training.
“This is still a medical tool requiring a prescription,” Hirsch said. “Patients must understand the lag time between blood and interstitial fluid. I cannot emphasize that enough, especially if the glucose is moving up or down quickly. The fingerstick [readings] will not match, because of that lag time. Lag time has improved over the years, but it is still there.”
Appropriate alarm settings on the device are also important to avoid issues like alarm fatigue, he said. Patients with poor glucose control should have their alarm threshold set higher.
“I had a patient who had her high alarm at 170 mg/dL, but her average was 160 mg/dL,” Hirsch said. “The whole point of a high alarm is when that goes off and you are taking insulin, you probably need more insulin. You can get alarm fatigue and not pay attention to it.”
Additionally, patients should understand trend arrows for each sensor and how to react with food or insulin dosing.
“Something I teach all of the fellows is that unless a person has had at least one professional CGM, you really do not know what their HbA1c means,” Hirsch said. “You need to do it at least once.”
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Hirsch I. Why should we use CHM in patients with type 2 diabetes? Assessing the evidence and practical pearls for integration. Presented at: Cardiometabolic Health Congress; Oct. 19-22, 2022; Boston.
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