Expanded CGM Access Could Usher in New Era of Diabetes Management

As the diabetes community approaches the 25th anniversary of the first US Food and Drug Administration (FDA) approval of a continuous glucose monitor (CGM) in 1999, it comes as the community is celebrating historic win in the fight for equitable access to technology and diabetes care.

In March of this year, the Centers for Medicare and Medicaid Services (CMS) announced a historic expansion of CGMs, with a change in eligibility requirements with a revision including people with diabetes who receive insulin treatment or have a history of problematic hypoglycemia in coverage. These changes went into effect on April 16.¹

“In my opinion, everyone would benefit from a CGM,” Christine Schumacher, PharmD, professor of Pharmacy Practice and director of the PGY2 Ambulatory Care Residency Program at Midwestern University College of Pharmacy, told HCPLive. “Honestly, I offer it to all people with diabetes that come into our clinic, whether or not it's going to be covered. That's something we talk about, I just let them know that this technology is there and it's evolving. It's available if they're interested.”

This change in policy by the CMS represents the second major change in the last 3 years after they eliminated their requirement of 4-times-daily fingersticks in order to qualify for coverage, in 2021.² Both changes pave the way for a new era made possible by the advances of the last 25 years.

A History of CGM Advances

In 1999, the FDA approved the Continuous Glucose Monitor System (CGMS) manufactured by Medtronic MiniMed. This system enabled recording of glucose values over a 3-day period, but was incapable of providing information the patient in real-time and required the provider to assess data after manual retrieval from the device.³

Medtronic continued to set the pace for innovation in the field early on, with the Medtronic Guardian introducing patients and clinicians to sensor-to-receiver wireless transmitting, as well as the use of programmable glucose alerts for both hypoglycemia and hyperglycemia in 2004.³

Later, in 2007, Dexcom would introduce the first device to allow for 7 days of continuous use. Abbott launched its FreeStyle Libre in the US in 2018 and offered users the ability to scan the receiver over the sensor to obtain current readings. EverSense found its way into treatment algorithms in 2016 with a 90-day sensor and, in 2017, offered users a sensor with an advertised lifespan of 180 days.³

In the last half-decade, these aforementioned companies and others have continued to drive the evolution of patient choice in diabetes technology by releasing numerous next-generation CGM systems boasting improved accuracy, smaller size, and other benefits.

“I liken it to how we think about the iPhone, right? The first iPhone was 2007 and we're already on version 15 and looking at 16,” Eugene Wright, MD, medical director for Performance Improvement at the Charlotte Area Health Education Center and consulting associate in the Department of Medicine at Duke University Medical Center, told HCPLive.

To fully understand the benefit CGM and enhanced glycemic control could provide at a population level requires a look back at the history of understanding of glycemic control on outcomes in people with diabetes.

Improved Glycemic Control Offers a Brighter Future

At the same time the community is preparing to celebrate the 25-year anniversary of the first professional use CGM in 2024, it is in the midst of celebrating the 40-year anniversary of the publishing of one of the most influential studies in the history of diabetes management: the Diabetes Control and Complications Trial (DCCT).

Launched in 1983 on behalf of the National Institute of Diabetes and Digestive and Kidney Diseases, the DCCT was created with the intent of assessing the effects of more intensive management of glycemic control on development and progression of neurologic complications in people with insulin-dependent, type 1 diabetes (T1D). The trial enrolled more than 1400 patients between the age of 13-39 years with none or minimal background retinopathy.⁴

Results of the trial, which were published in the New England Journal of Medicine in September 1993, suggested intensive therapy was associated with a 76% reduction in the relative risk of developing retinopathy in adjusted analyses with a mean follow-up of 6.5 years. Further analysis found intensive therapy was associated with a 39% reduction in the occurrence of microalbuminuria, a 60% reduction in clinical neuropathy, and a 54% reduction in albuminuria.⁴

As a result of the DCCT and evolutions in technology during the late 1980s and early 1990s, the Epidemiology of Diabetes Interventions and Complications (EDIC) study was launched in 1993 with the aim of the long-term effects, including cardiovascular events, among this same cohort. In 2013, results of the study, which included 30 years of follow-up from the DCCT and EDIC studies, concluded intensive therapy was associated with a 30% relative reduction in risk of any cardiovascular disease and a 32% reduction in relative risk of major cardiovascular events, with investigators suggesting lower HbA1c levels accounting for all of the observed treatment effect on cardiovascular disease risk.⁵

Rose Gubitosi-Klug, MD, PhD, the William T. Dahms Chair in Pediatric Endocrinology and division chief of Pediatric Endocrinology at UH Rainbow Babies and Children’s Hospital, currently serves as the principal investigator in her hospital’s role as the national clinical coordinating center for DCCT/EDIC. In a statement, she explained how improved management over time provides continuous and long-lasting effects for patients—even decades later.⁶

“We can not only prevent the onset of complications, we can also make an impact in secondary prevention, slowing the progression,” Gubitosi-Klug said.⁶ “So if for the first 20 years of your type 1 diabetes diagnosis you struggle, if you improve, then 30 and 40 years out, it still gives you benefit.”

With this enhanced understanding of the benefit in hand, the community has endeavored further towards optimized management of both type 1 and type 2 diabetes. So much so, it has begun to evolve beyond use of HbA1c. Once the gold standard for quantifying glycemic control, and still the primary outcome measure for most major trials, it is now regarded by many as a dated metric with limited insight into glycemic control as a result of its stagnant nature. At the same time, the concept of time-in-range has gained steam as the most appropriate metric, to-date, for assessing glycemic control.

In 2019, the American Diabetes Association published its recommendation for time-in-range, including 70-180 mg/dl (3.9-10.0 mmol/L) for people with type 1 or type 2 diabetes. This also included outlines of thresholds to identify time below and time above range.⁷ More recently, as a result of improved management practices and technology, some have begun to champion time in tighter range as a means for quantifying glycemic control.

The Future for CGM

Most involved in the management of diabetes have, over time, become staunch advocates for expanding use to all people with diabetes and insulin users with a desire for access to such technology. However, the benefit of understanding glycemic control has proven so useful it has attracted the attention of other specialists for its potential uses.

Among the most obvious first destinations for the technology are in use by dietitians and nutritionists. As the medical community learns more about insulin resistance and metabolic disease, some argue use in patients with symptoms of insulin resistance could improve management for a multitude of conditions.

“Once we start to integrate fully into the patients or people with diabetes population, I think we're going to start to see it more in prediabetes. I think it’ll be really helpful in diet and education management,” Schumacher said. “I know our dietitians love it, they can have real great conversations just based on what spikes their numbers.”

However, some have already begun to hypothesize and experiment in roles beyond traditional healthcare and disease management. Perhaps the most high-profile use of CGM in someone not using insulin and without diabetes was Abbott’s 2021 campaign where the company provided Libre Sense Glucose Sport Biosensors to a team of marathoners with the goal of improving athletic performance.⁸

Although the possibility of significant expansion into patient populations without diabetes seems imminent at some point in the future, experts remain adamant the focus should remain on people with diabetes and insulin users before expanding beyond these patient populations, whether through CMS coverage or other means.

“I would hope the first place that this would go is just gaining more access for people that have diabetes…I would argue that is where we will go first, but do I think we're going to use it in patients without diabetes in the very near future?” Cara Liday, PharmD, associate professor in the Department of Pharmacy Practice at Idaho State University, said. “I don't just because we need better access to (it) and we need better technology for those that have diabetes.”

References

1. ^{Isaacs D, Bellini N. Diabetes Dialogue: CMS expansion ushers in new age of CGM access. HCP Live. March 17, 2023. Accessed July 5, 2023. https://www.hcplive.com/view/diabetes-dialogue-cms-expansion-ushers-in-new-age-of-cgm-access.}
2. ^{American Diabetes Association. New Medicare coverage requirements make CGMS more accessible. New Medicare Coverage Requirements Make CGMs More Accessible | ADA. Accessed July 5, 2023. https://diabetes.org/tools-support/devices-technology/cgm-medicare-coverage-requirement-change-accessibility.}
3. ^{Didyuk O, Econom N, Guardia A, Livingston K, Klueh U. Continuous Glucose Monitoring Devices: Past, Present, and Future Focus on the History and Evolution of Technological Innovation. J Diabetes Sci Technol. 2021;15(3):676-683. doi:10.1177/1932296819899394}
4. ^{Diabetes Control and Complications Trial Research Group, Nathan DM, Genuth S, et al. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329(14):977-986. doi:10.1056/NEJM199309303291401}
5. ^{Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) Study Research Group. Intensive Diabetes Treatment and Cardiovascular Outcomes in Type 1 Diabetes: The DCCT/EDIC Study 30-Year Follow-up. Diabetes Care. 2016;39(5):686-693. doi:10.2337/dc15-1990}
6. ^{University Hospitals. DCCT edic at 40 uh rainbow plays pivotal role in landmark type 1 diabetes study. DCCT EDIC at 40 UH Rainbow Plays Pivotal Role in Landmark Type 1 Diabetes Study | University Hospitals. February 26, 2023. Accessed July 5, 2023. https://www.uhhospitals.org/for-clinicians/articles-and-news/articles/2023/02/dcct-edic-at-40-uh-rainbow-plays-pivotal-role-in-landmark-type-1-diabetes-study.}
7. ^{Battelino T, Danne T, Bergenstal RM, et al. Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range. Diabetes Care. 2019;42(8):1593-1603. doi:10.2337/dci19-0028}
8. ^{Abbott. World’s fastest marathoner Eliud Kipchoge uses Abbott’s Libre Sense at NN mission marathon qualifier race for the Olympic Games. Abbott MediaRoom. April 12, 2021. Accessed July 5, 2023. https://abbott.mediaroom.com/2021-04-12-Worlds-Fastest-Marathoner-Eliud-Kipchoge-Uses-Abbotts-Libre-Sense-at-NN-Mission-Marathon-Qualifier-Race-for-the-Olympic-Games.}