4.5.0.0 Intermittently Scanned Continuous Glucose Monitor Use
Recommendation
7.19 Intermittently scanned continuous glucose monitor use may be considered as a substitute for self-monitoring of blood glucose in adults with diabetes requiring frequent glucose testing. C
isCGM (sometimes referred to as “flash” CGM) is a CGM that measures glucose in interstitial fluid through a <0.4 mm– thick filament that is inserted under the skin. It has been available in Europe since 2014 and was approved by the FDA for use in adults in the U.S. in 2017. The personal version of isCGM has a receiver that, after scanning over the sensor by the individual, displays real-time glucose values and glucose trend arrows. The data can be uploaded and a report created using available software. In the professional version, the patient does not carry a receiver; the data are blinded to the patient and the device is downloaded in the diabetes care provider’s office using the provider’s receiver and the software. The isCGM sensor is smaller than those of other systems and is water resistant. In the U.S., the FDA now requires a 1-h start-up time after activation of the system, and it can be worn up to 14 days. The isCGM does not require calibration with SMBG because it is factory calibrated. Acetaminophen does not cause interference with glucose readings. The mean absolute relative difference reported by the manufacturer is 9.4%. It measures glucose every minute, records measurements every 15 min, and displays up to 8 h of data. As opposed to real-time CGM systems, isCGM has no alarms. The direct costs of isCGM are lower than those of realtime CGM systems. In general, both the consumer and professional versions are covered by most commercial insurance carriers and eligible Medicare programs. Information on Medicaid coverage was not available at the time of this writing.
Studies in adults with diabetes indicate isCGM has acceptable accuracy when compared with SMBG (99–102), although the accuracy may be lower at high and/or low glucose levels (103,104). Studies comparing the accuracy of isCGM with real-time CGM show conflicting results (102,104,,105). isCGM may decrease the risk of hypoglycemia in individuals with type 1 (85) or type 2 diabetes (94). There are a growing number of studies suggesting similar good performance and potential for benefit in special populations, including pregnant women with diabetes (106), individuals with type 1 diabetes and hypoglycemia unawareness(107), and children (108–110), although accuracy (mean absolute relative difference) could be decreased in younger children (109). Contact dermatitis has been reported and linked to the presence of isobornyl acrylate, a structural plastic of the device, which is a skin sensitizer and can cause an additional spreading allergic reaction (111–113).
There are several published reviews of data available on isCGM (114–116). The Norwegian Institute for Public Health conducted an assessment of isCGM clinical effectiveness, cost-effectiveness, and safety for individuals with type 1 and type 2 diabetes, based on data available until January 2017 (114). The authors concluded that, although there were few quality data available at the time of the report, isCGM may increase treatment satisfaction, increase time in range, and reduce frequency of nocturnal hypoglycemia, without differences in A1C or quality of life or serious adverse events. The Canadian Agency for Drugs and Technologies in Health reviewed existing data on isCGM performance and accuracy, hypoglycemia, effect on A1C, and patient satisfaction and quality of life and concluded that the system could replace SMBG in particular in patients who require frequent testing (115). The last review published at the time of this report (116) also supported the use of isCGM as a more affordable alternative to real-time CGM systems for individuals with diabetes who are on intensive insulin therapy.