Barbara Onumah, Medical Director, diabetes and endocrinology, Anne Arundel Medical Center
Physicians treating people with diabetes (PWD) are often placed in the position of making treatment and medication adjustments solely on hemoglobin A1C (A1C) levels. A1C and finger stick blood glucose data were the best options we had for many years but lacked important detail such as high and low glucose excursions, trends, and variabilities to allow informed management decisions. Continuous Glucose Monitors (CGM) enables not only providers but PWD this data to be used retrospectively and real time. CGM systems consist of a tiny electrode or a sensor placed under the skin with an inserter, a transmitter and a receiver. The receiver can be a smart phone, an insulin pump, or a designated receiver for the CGM system. Most sensors last 10 to 14 days and are inserted by the user.
Sensor reading include trend arrows which let the user know glucose trends at all times. The glucose trends include:
• Glucose is steady
• Glucose is moderately trending up/down = changing 30 to 60mg/dL in the next 30 minutes
• Glucose is rapidly trending up/down = 60 to 90 mg/dL in the next 30 minutes
• Glucose is extremely rapidly trending up/down = more than 90mg/dL in the next 30 minutes.
The ability of sensors to monitor glucose trends has allowed them to be integrated with insulin pumps to create “smart pumps”. The pumps have algorithms that determine automated insulin adjustments based on the current glucose level and their trends.
"CGMs play a movie of blood glucoses as compared to snapshot picture of finger stick glucose"
CGMS can be downloaded and multiple reports can be generated by the healthcare professional and users. For busy providers, the CGM ambulatory glucose profile (AGP) report allows assessment of multiple metrics over a defined period on one page. Standardized targets for most adults with diabetes have been established for these metrics. The Time in Range (TIR) section of the report allows a quick view of all the glucose levels and excursions divided into 5 categories.
• Time in Range (TIR) is defined as the percentage of time the glucose readings were between 70 – 180 mg/dL with a clinical target of over70 percent.
• Time Above Range (TAR) level 1 is defined as the percentage of time the glucose readings were between 180 – 250 mg/dL with a clinical target of under 25 percent.
• TAR level 2 is defined as the percentage of time the glucose readings where greater than250mg/dL with a clinical target of less than 5 percent.
• Time Below Range (TBR) level 1 is defined as the percentage of time the glucose readings were 54 – 69mg/dL with a clinical target of less than 4 percent.
• TBR level 2 is defined as the percentage of time the glucose readings were lesser than 54mg/dL with a clinical target of less than 1 percent.
A busy provider can quickly assess the need to further investigate hypoglycemia and hyperglycemia events with the TIR report. The provider can then review the AGP graph to identify the time of day that low and high glucose levels, trends and excursions are occurring. The AGP report can also give an estimate of the A1C level based on glucose measured for a given time period. This is called the glucose management indicator (GMI). The glucose variability (%CV) indicates glucose variability with a clinical guideline target of less than 36 percent. AGP report can help providers assess glucose management, make treatment decisions, guide discussions with PWD and help them set individualized goals. The PWD can then watch over time as they move closer to their goals not only during provider visits but between visits and even daily.
PWD are sometimes resistant to trying a CGM because they do not want a device attached to them and may not understand how the CGM can assist with ongoing diabetes self-management. They are often encouraged to wear the sensors for a short time and if they do not like it, they can always go back to monitoring with glucose meter. Needless to say, patients’ try it and fall in love wanting their own CGM. They report lifestyle changes they have already made by seeing the glucose responses to variables such as food choices, activity, insulin doses or timing of doses just to mention a few. CGMs play a movie of blood glucoses as compared to snapshot picture of finger stick glucose. A common saying of one of the diabetes educator on our team who wears a sensor is “without my sensor, I feel like I am stranded in the middle of the ocean without a life jacket”
With all the assistance CGMs can provide with diabetes management, I wonder why every PWD does not have their own CGM. Patient resistance and clinician inertia may be reasons, but mostly it is due to insurance coverage or lack thereof. Insurance plans have different requirements for coverage with out- of -pocket tiers that can make CGMs cost prohibitive. This is truly unfortunate as the CGM has elevated glucose monitoring and added additional layer of meaning. CGM companies can do their part by ensuring that marketing does not only focus on its convenience to reduce finger sticks but most importantly highlight the benefit of getting more glucose data to direct therapeutic and lifestyle decision.
Hesham Abboud, MD, PhD, Director of the Multiple Sclerosis and Neuroimmunology Program and staff neurologist at the Parkinson’s and Movement Disorder Center at University Hospitals of Cleveland, Case Western Reserve University School of Medicine