Over the past decade, continuous glucose monitoring (CGM) has reshaped the standard of care for much of the diabetes community, but debate continues about the benefits, weaknesses, and interpretation of the data these devices provide.

A panel of experts will critically examine some of these issues during the symposium, Controversies in Continuous Glucose Monitoring, on Friday, June 20, from 3:45–5:15 p.m., in Room W183 BC of the McCormick Place. On-demand access to recorded presentations will be available to registered participants following the conclusion of the 85^th Scientific Sessions, from June 25–August 25.

Michael Kohn, MD, MPP, Professor of Epidemiology & Biostatistics in the School of Medicine at University of California, San Francisco, will open the session with an overview of the prevalence, strengths, and limitations of leading prescription CGM devices.

CGM technology provides less accurate blood glucose readings than fingerstick monitors and may miss significant hypoglycemic events, he noted. Nonetheless, prescription CGMs have had a positive overall impact on care for individuals with diabetes.

“There is really no controversy about the accuracy of CGMs,” Dr. Kohn said. “They are not as accurate as fingerstick readings and are especially inaccurate when the blood glucose is low. Despite this, in ambulatory outpatients, glucose control is clearly better with CGMs, according to multiple metrics, including frequency of hypoglycemic events. Glucose control is better yet when the CGM is part of an automated insulin delivery (AID) system, used by more than half of Americans living with type 1 diabetes.”

Dr. Kohn will discuss how some debates—and future research opportunities—exist around the applicability of CGMs for patients in hospitals or for pregnant women when gestational diabetes is a concern.

An expert in diagnostic and prognostic testing, Dr. Kohn will also cover the primary CGM accuracy metrics: the mean absolute relative difference (MARD), the agreement rate (AR), percent in Zone A of an error grid, and true detection/false alarm rate for hypo/hyperglycemia.

Nicole Ehrhardt, MD, said it was important for clinicians to understand how to interpret these types of data from CGMs and to be able to explain the data to patients in plain language.

“CGMs provide benefits and knowledge to both the wearer and the clinician, but there are inaccuracies,” said Dr. Ehrhardt, Assistant Professor at the University of Washington and Endocrinologist at the University of Washington Diabetes Institute. “There are inaccuracies in A1C readings as well as in the GMI (glucose management indicator) readings, and so we want to look at the whole patient picture, understand these shortcomings, and use all our tools to best assess a patient’s health and to empower them.”

Many people still mistakenly equate GMI with A1C readings, she noted. Understanding the differences between the two can help clinicians and device wearers to recognize when GMI might be a preferable tool, such as for monitoring people with chronic kidney disease (CKD), a known population where A1C is inaccurate, Dr. Ehrhardt said.

Tadej Battelino, MD, PhD, Clinical Pharmacologist, Consultant, and Head of Department of Endocrinology at University Children’s Hospital-University Medical Center Ljubljana, Slovenia, and Head/Chair of Pediatrics in the Faculty of Medicine at University of Ljubljana, will examine other limitations of A1C. He will also outline why A1C’s emphasis on a patient’s 100-day mean glucose reading and its dependency on an individual’s glycation enzyme capacity makes it an inferior tool to time in range (TIR) and rime in right range (TITR) readings available through CGMs.

“The major advantage of CGM-derived metrics is that they are actionable,” Dr. Battelino said. “People with diabetes see their TIR continuously and can improve and get to their target.”

Dr. Battelino noted CGMs benefit people with different types of diabetes in different ways.

For people with type 1 diabetes, CGM data can help identify early stages of the disease and help them avoid diabetes-related ketoacidosis (DKA). When CGMs are integrated into AID systems, they considerably improve the glycemic outcomes and reduce the disease burden for those with type 1 diabetes.

For people with or at risk for type 2 diabetes, CGMs and their data are “game changers,” Dr. Battelino said.

“In the clinics, we should be telling people, ‘Your percentage of time above range is dangerous. We have medications to reverse this and protect you from developing type 2 diabetes.’  This should be the conversation, and in years to come, this will result in a significant reduction of type 2 diabetes and its consequences, particularly dementia and cardiovascular complications,” Dr. Battelino said. “We have a chance to change the course of this disease and to help people retain a healthy longevity.”