CGM

Continuous Glucose Monitor (CGM)

Background

A classical marker for disease control in the care of patients with diabetes has been hemoglobin A1c which measures the average blood sugar levels over the last 3 months by measuring the gly, however it fails to capture the fluctuations in blood sugar that a patient experiences. Continuous glucose monitoring (CGM) first approved by the FDA in 19991 works through a subcutaneous sensor which measures the glucose levels found in the fluid between cells known as interstitial glucose levels. This continuous capture of glucose levels reveals glucose fluctuations previously not captured. In fact, the lower time in range (TIR) derived from CGM information, indicating poor disease control, shows association with all studied microvascular and macrovascular complications2. Additionally, since initial approval, CGM has shown “to improve glycemic control, reduce hypoglycemia, lower glycemic variability and enhance the quality of life” 3.

Current US Market

• Endo.Digital - link Dexcom

• Abbott – Freestyle Libre (Continuous Glucose Monitoring (CGM) | FreeStyle Libre (CGM) systems)

• Medtronic – Guardian (Guardian Connect Continuous Glucose Monitoring | Medtronic (medtronicdiabetes.com))

Implanted Devices: Eversense (Reference: Eversense E3 Continuous Glucose Monitoring System - P160048/S016 | FDA)

Comparison of devices is available here CGM Device Comparison | American Association of Clinical Endocrinology (aace.com).

Professional versus Personal CGM

CGMs are categorized as either professional or personal. This designation is created based on who owns the device. For professional CGM (Pro CGM) the CGM is owned by the clinic. This can come in two formats blinded and unblinded. In blinded set up the patient does not see the readings while wearing the sensor, instead the aggregate results are reviewed after collecting data for 1-2 weeks the results are reviewed by the patient and provider together. This allows for collection of blood glucose information without patient interacting with the information. (How Can a Professional CGM Help You? (diatribe.org) and Personal Versus Professional Continuous Glucose Monitoring: When to Use Which on Whom - PMC (nih.gov))

Implementation

Despite the opportunity for CGM to improve the care of patients with diabetes, this technology remains underutilized especially in historically marginalized populations4. Significant disparities in the use of diabetes technologies exists and appear to be related to “inequitable prescribing practices, lack of support for social determinants of health, mismatch of patient preferences and care models, and cost.” 5 While insurance coverage and requirements limited some patient’s access to this technology initially6, nationally this is changing (New Medicare Coverage Requirements Make CGMs More Accessible | ADA (diabetes.org)). In 2020, The Association of Diabetes Care & Education Specialists published the Personal Continuous Glucose Monitoring Implementation Playbook7 which identified 11 steps for successful CGM implementation in the clinical environment. In 2022 over 130 individuals from more than 60 organizations came together to participate in a yearlong project (The Launch of the iCoDE Standard Project - PubMed (nih.gov)) which resulted in the creation of the 2022 iCoDE Report: CGM-EHR Integration Standards and Recommendations which is helping to guide CGM-EHR integration work Diabetes Technology Society.

Resources for Prescribers

AAFP - Continuous Glucose Monitoring | AAFP

Next Steps

While CGM allow for incredible opportunity for empowering patients to understand and manage their disease process, significant work remains to optimize the use of this technology in the clinical setting to ensure optimal use to impact clinical outcomes and ensure equitable access. This remains an area of critical importance for clinical informatics as data flow, standards, technology, patient use, clinical decision support, policy, and legal frameworks all come together in this space.

References

1. 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. 2. Yapanis M, James S, Craig ME, O'Neal D, Ekinci EI. Complications of Diabetes and Metrics of Glycemic Management Derived From Continuous Glucose Monitoring. J Clin Endocrinol Metab. 2022;107(6):e2221-e2236. 3. Edelman SV, Cavaiola TS, Boeder S, Pettus J. Utilizing continuous glucose monitoring in primary care practice: What the numbers mean. Prim Care Diabetes. 2021;15(2):199-207. 4. Isaacs D, Bellini NJ, Biba U, Cai A, Close KL. Health Care Disparities in Use of Continuous Glucose Monitoring. Diabetes Technol Ther. 2021;23(S3):S81-s87. 5. Agarwal S, Simmonds I, Myers AK. The Use of Diabetes Technology to Address Inequity in Health Outcomes: Limitations and Opportunities. Curr Diab Rep. 2022;22(7):275-281. 6. McAdam-Marx C. Addressing healthcare disparities and managed care considerations with continuous glucose monitoring. Am J Manag Care. 2022;28(4 Suppl):S76-s84. 7. Specialists TAoDCE. The ADCES and APhA/APhA Foundation Personal CGM Implementation Playbook. 2020; https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/cgm-playbooks/apha-adces-personal-cgm-playbook_kbedits0921pdf5e8e8e42-8283-465e-ab8c-bd8399cc1eab.pdf?Status=Master&sfvrsn=8b8b9e58_5.

Submitted by Michelle Knopp