Continuous Glucose Monitoring Systems

Key Characteristics and Usage

• The American Diabetes Association recommends using intermittently scanned CGM systems, such as the Freestyle Libre, which has key characteristics including data obtained by scanning the sensor with a reader device rather than continuous transmission 1
• The American Diabetes Association suggests that for intermittently scanned CGM like Libre, the device should be scanned at minimum once every 8 hours to capture complete 24-hour data 1
• The Freestyle Libre is one of the most commonly used continuous glucose monitoring (CGM) systems, specifically categorized as an intermittently scanned CGM (isCGM) system, according to the International Journal of Behavioral Nutrition and Physical Activity and Diabetes Care 2, 1

Indications and Recommendations

• Continuous glucose monitoring (CGM) devices are recommended by the American Diabetes Association for patients with type 1 diabetes, those with type 2 diabetes on intensive insulin therapy, and pregnant women with diabetes, as they can effectively lower A1C levels and reduce hypoglycemia risk 3, 4, 5
• The American Diabetes Association suggests that CGM devices are beneficial for patients with significant glycemic variability and those experiencing problematic hypoglycemia, with the greatest mortality and morbidity benefit seen in these populations 5
• The American Diabetes Association does not recommend CGM devices for patients with type 2 diabetes treated with diet and/or oral agents alone 6
• Patients in intensive care settings, individuals unwilling to learn the basic mechanical skills of the equipment, and those with certain medical conditions (e.g. skin edema, vasoconstrictor drugs, hypotension or hypoxemia) are not recommended for CGM devices 5, 7

Device Operation and Maintenance

• Proper education and training on device use is essential for effective CGM device operation 7
• Calibration values should be entered immediately after obtaining them, using the same glucose meter and batch of test strips 5
• Users should be aware of potential interfering substances, such as uric acid, galactose, and acetaminophen, which can affect glucose oxidase monitors 7
• Skin reactions, such as irritation or allergy, should be assessed and addressed 3

Data Interpretation and Management

• Real-time CGM data is considered valid if the system has been worn for at least 12 hours, is adequately calibrated, and has no false alarms 5
• Users should record diet, exercise, medication, and other relevant events in detail to make informed decisions about food intake and insulin dosing 5
• When evaluating CGM data, focus on time in range (70-180 mg/dL), time below range, and glycemic variability 5, 8

Specific Devices and Technologies

• FreeStyle Libre 3 provides real-time glucose readings without requiring fingerstick calibration, with an overall MARD of 7.8% compared to venous blood glucose reference 1
• The American Diabetes Association recommends Freestyle Libre for adults with Type 1 diabetes on multiple daily injections or insulin pump therapy, adults with Type 2 diabetes on basal insulin or multiple daily injections, and youth with Type 1 diabetes 9
• Proper prescribing signature for Freestyle Libre: "Freestyle Libre sensor, apply one sensor every 14 days to back of upper arm, scan as needed for glucose monitoring" 9

Clinical Benefits and Outcomes

• Reduction in hypoglycemia time and severity has been observed with the use of FreeStyle Libre 3 1
• Improved glycemic control without increasing hypoglycemia risk can be achieved with CGM 1, 5
• The American College of Endocrinology notes that CGM can help identify hypoglycemia patterns that may be missed with traditional monitoring methods 8, 10

Reimbursement and Access

• Medicare Part B covers CGM devices and supplies for beneficiaries with diabetes requiring intensive insulin management, including patients with Type 1 diabetes and those with Type 2 diabetes on multiple daily injections or insulin pump therapy 11, 5
• Medicare Part B also covers CGM for beneficiaries with specific clinical needs such as unexplainable severe hypoglycemia, recurrent hypoglycemia, and nocturnal hypoglycemia 11, 5

Follow-up and Ongoing Management

• Professional CGM use should always be coupled with analysis, interpretation, and education 12
• Schedule follow-up within 2-4 weeks of initial prescription to review data and adjust insulin regimen as needed 1
• Regular review of CGM data is necessary to evaluate the effectiveness of dose adjustments and assess glycemic control, as recommended by the International Diabetes Federation 12, 8