Scanning a continuous glucose monitoring (CGM) system intermittently led to improved blood glucose control compared with traditional finger-stick glucose testing in people with type 1 diabetes, according to a new study published in the New England Journal of Medicine.
Most CGM systems take glucose readings at a defined interval — typically every five minutes or every minute — and send these readings to a dedicated device or smartphone app. But some CGM systems also allow users to scan their sensor with a device for an immediate reading, with or without automatic readings. In some European countries, it’s common for people with type 1 diabetes to use CGM systems configured so that glucose readings are always manually scanned, with alarms enabled in case glucose levels become dangerously high or low. Used this way, approved CGM systems can act as a substitute for finger-stick testing.
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For the latest study, researchers recruited 156 participants with type 1 diabetes and an A1C level (a measure of long-term blood glucose control) between 7.5% and 11.0%, indicating higher-than-desired blood glucose levels. The average age of participants at the start of the study was 44, and their average duration of diabetes was 21 years. Participants were randomly assigned either to continue with their regular finger-stick blood glucose testing, or to use intermittent scanning with a CGM system, for 24 weeks. Each of the two study groups had 78 participants, and members of both groups wore a CGM system that continually recorded their glucose levels — but neither group could see these ongoing glucose readings. Only members of the intermittent scanning group had access to optional alarms for high or low glucose levels.
Intermittent CGM scanning linked to better glucose control
At the beginning of the study, the average A1C level in the finger-stick group was 8.5%, and in the intermittent scanning group it was 8.7%. After 24 weeks of their assigned method of blood glucose testing or scanning, the average A1C level dropped slightly to 8.3% in the finger-stick group, while in the intermittent scanning group it fell to 7.9% — a greater A1C reduction by 0.5% in the intermittent scanning group. The intermittent scanning group also spent an average of 9% more time each day in their target glucose range, or 130 more minutes each day. What’s more, the intermittent scanning group spent an average of 3% less time each day, or 43 fewer minutes, with a blood glucose level below 70 mg/dl.
Two members of the finger-stick group experienced severe hypoglycemia (low blood glucose) over the course of the study, compared with none in the intermittent scanning group. One member of the intermittent scanning group had a skin reaction to the glucose sensor.
The researchers concluded that in this study population with type 1 diabetes, intermittent scanning with a CGM system was linked to significantly better blood glucose control than finger-stick blood glucose testing — suggesting that intermittent scanning may be a worthwhile alternative to traditional blood glucose testing. Further studies would be needed to demonstrate this benefit in people with type 2 diabetes, or in a population with different traits such as youth with type 1 diabetes.
Want to learn more about managing blood glucose? See our “Blood Sugar Chart,” then read “What Is a Normal Blood Sugar Level?” and “Strike the Spike II: How to Manage High Blood Glucose After Meals.”