Today our very own APD and endocrinologist extraordinaire Dr. Trish Santos presented an amazing talk on “Glucose Monitoring for the Internist: A Growth Mindset.”
We started with a discussion of the history of glucose monitoring since the 1950s into the current state of continuous glucose monitors (CGMs). This lead to a review of the use of hemoglobin A1c as a screening and monitoring tool for diabetes mellitus. Dr. Santos highlighted that the A1c is especially helpful from a population level and for predicting microvascular damage, but has some issues for individual patients. Current assays have a margin of error of 0.5%, and with data provided by CGM, it has been shown that the previous assumed fasting blood glucose (BG) levels may not actually reflect the true range of daily glucose variability in an individual. We reviewed some of this variability by looking at two patient examples and also discussed some of the reasons for variability in hemoglobin A1c.
We then started discussing the role of self-monitored blood glucose (SMBG) checks, which really only seems to have a role in patients on insulin therapy. Dr. Santos highlighted many of the challenges that patients face when using SMBG, which can be extensive! In addition to the challenges, we also discussed that the SMBG can give people false assurance about the true value of BG levels – it is not the gold standard for BG levels (plasma BG is the gold standard)!
Dr. Santos then completed her talk with a discussion of the CGM specifically. The CGM has 3 components: a subcutaneous glucose sensor, a transmitter, and a receiver (usually via a smart phone/device). Between devices, the mean absolute relative difference (MARD) is used, which assesses the accuracy between devices for BG monitoring. Dr. Santos then reviewed the most common devices available for our patients, with some important distinctions and caveats between devices (check out the summary table below). We discussed that the likely future of CGM will be an implantable sensing device that lasts for up to 90 days (newly available at UCSD)! Finally, we reviewed how CGMs can be used for data acquisition and for therapeutic intervention for type 2 diabetics. The use of CGM has been shown to improve both average BG levels and has lead to improved patient satisfaction as well! We are also slowly working on how to utilize the data provided by these devices, which is an ongoing, but exciting prospect!