Some factory-calibrated continuous glucose monitoring (CGM) systems are approved for non-adjunctive use, although these systems require adjunctive self-monitored blood glucose (SMBG) tests in specific instances. We estimated how often users of an intermittently-scanned CGM (isCGM) system might be required to perform SMBG testing. Criteria under which an adjunctive SMBG test is required were obtained from the U.S.-specific 14-day isCGM user guide (Figure). Real-world glucose values were obtained from a random sample of 10,000 adults (ages 18+) who used Dexcom G6 real-time CGM at least 90% of the time for at least 14 days between 7/1/2018-9/30/2018. The percentage of values meeting one or more of the criteria for mandatory SMBG testing was calculated as hours per day. Glucose readings were changing > 2 mg/dL/min a mean (SD) of 1.34 (0.77) hours/day, predicted to be < 70 mg/dL within 15 minutes for 1.03 (0.95) hours/day, and < 70 mg/dL for 0.67 (0.79) hours/day; one or more of these criteria were present for 2.35 (1.30) hours/day. Added to the 0.86 hour/day warmup period, SMBG testing would be indicated for an isCGM user for an average of 3.20 (1.30) hours/day. This may be a conservative estimate as the isCGM label demonstrates that the system overestimates hypoglycemia. Users of the isCGM system are likely to confront multiple intervals during which SMBG is required and reliance on their isCGM glucose values for diabetes management decisions is contraindicated.


D.A. Price: Employee; Self; Dexcom, Inc. Stock/Shareholder; Self; Johnson & Johnson.

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