Background: Continuous glucose monitoring (CGM) is an emerging technology that provides real-time interstitial glucose levels through a sensor with a thin filament inserted under the skin. It is customary for patients to rotate sensor application sites between arms to minimize skin irritation. However, the degree of inter-arm differences with CGM technology remains unknown.

Materials and Methods: Self-proclaimed right-handed (n=5) and left-handed (n=5) subjects, regardless of concurrent comorbidities, were enrolled for CGM. A FreeStyle Libre Pro Flash Glucose Monitoring System sensor was simultaneously placed on each arm for all subjects. The sensors were worn for a maximum of 14 days with measurements taken every 15 minutes. Muscle mass and body fat analysis was conducted using a multi-frequency segmental body composition analyzer. Glucose levels from the right and left arms were time-matched with the first 12 hours eliminated from analysis.

Results: A total of 9830 paired glucose levels were included for analysis. Glucose levels were outside the euglycemic range (70-140 mg/dL) for 14.5% of the time in the right arm compared to 20.0% in the left arm (P<0.001). The glucose level in the right arm was higher than the left arm in 67% (range 46 - 98%) of the measurements (P<0.001). The absolute difference in glucose level between the right and left arms was >10 mg/dL, >20 mg/dL, and >30 mg/dL, for 19.4%, 3.4%, and 0.32% of the time, respectively. The mean glucose level in the right arm was higher than the left arm by 3.75 mg/dL [SD, 8.51 mg/dL] in right-handed subjects, and by 3.84 mg/dL [SD, 7.09 mg/dL] in left-handed subjects (P=0.54).

Conclusion: Time in euglycemic range could significantly differ based on arm selection when using a CGM. While the absolute difference in glucose levels between arms appears small, this degree of variability would have significant implications for clinical trial design using CGM technology. Arm dominance does not explain the inter-arm glucose level discordance.


N. Kim: None. K. Pham: None. A. Shek: None. J.J. Lim: Employee; Self; Genentech, Inc. Stock/Shareholder; Self; F. Hoffmann-La Roche Ltd. S.A. Shah: None.


University of the Pacific

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