Decision accuracy of simultaneously used real‐time CGM versus intermittently scanned CGM around exercise in type 1 diabetes: A secondary analysis of the ULTRAFLEXI‐1 study

AIMS Continuous glucose monitoring (CGM) systems have become important technologies to improve glycaemia in people with type 1 diabetes (T1D). However, it has been shown that during rapid glucose change, sensor performance can deteriorate. Comparative data on sensor performance during high rates of glucose change, such as during exercise, between a real-time continuous glucose monitor (rtCGM) and an intermittently scanned continuous monitor (isCGM) remain limited.

METHODS Twenty-two people with T1D (8 women, age 42 ± 11 years, HbA1c 59 ± 8 mmol/mol (7.6 ± 0.8%)) simultaneously used an rtCGM (Dexcom G6) and an isCGM (Freestyle Libre 1). Sixty-minute exercise sessions were performed on a cycle ergometer at moderate intensity, and glucose values from both CGM systems were compared against capillary reference blood glucose measurements (EKF S-Line; EKF Diagnostics, Germany). Data were assessed using the Median Absolute Relative Difference (MedARD) with interquartile range, as well as the Diabetes Technology Society Error Grid (DTS EG).

RESULTS During exercise, the MedARD was 14.6% [7.0;23.8] for rtCGM (2304 comparison points) vs. 11.6% [5.6;19.6] for isCGM (2266 comparison points) (p < 0.0001). When stratified by glycaemic range, the MedARD was 39.2% [31.8;46.8] vs. 27.0% [17.0;34.6] for time below range (<70 mg/dL) (p = 0.0001), 16.1% [8.1;24.8] vs. 12.8% [6.4;20.4] for time in range (70-180 mg/dL) (p < 0.0001) and 9.5% [4.7;16.0] vs. 8.0% [3.8;13.7] for time above range (>180 mg/dL) (p = 0.0064) for rtCGM vs. isCGM.

CONCLUSION In this head-to-head comparison of rtCGM and isCGM, isCGM demonstrated superior performance during exercise in adults with T1D.