Accuracy and Reliability of Continuous Glucose Monitoring Systems: A Head-to-Head Comparison

Objective: This study assessed the accuracy and reliability of three continuous glucose monitoring (CGM) systems. Research Design and Methods: We studied the Animas (R) (West Chester, PA) Vibe (TM) with Dexcom (R) (San Diego, CA) G4 (TM) version A sensor (G4A), the Abbott Diabetes Care (Alameda, CA) Freestyle (R) Navigator I (NAV), and the Medtronic (Northridge, CA) Paradigm (R) with Enlite (TM) sensor (ENL) in 20 patients with type 1 diabetes mellitus. All systems were investigated both in a clinical research center (CRC) and at home. In the CRC, patients received a meal with a delayed and increased insulin dose to induce a postprandial glucose peak and nadir. Hereafter, randomization determined which two of the three systems would be worn at home until the end of functioning, attempting use beyond manufacturer-specified lifetime. Patients performed at least five reference finger sticks per day. An analysis of variance was performed on all data points 15min apart. Results: Overall average mean absolute relative difference (MARD) (SD) measured at the CRC was 16.5% (14.3%) for NAV and 16.4% (15.6%) for ENL, outperforming G4A at 20.5% (18.2%) (P < 0.001). Overall MARD when assessed at home was 14.5% (16.7%) for NAV and 16.5 (18.8%) for G4A, outperforming ENL at 18.9% (23.6%) (P = 0.006). Median time until end of functioning was similar: 10.0 (1.0) days for G4A, 8.0 (3.5) days for NAV, and 8.0 (1.5) days for ENL (P = 0.119). Conclusions: In the CRC, G4A was less accurate than NAV and ENL sensors, which seemed comparable. However, at home, ENL was less accurate than NAV and G4A. Moreover, CGM systems often show sufficient accuracy to be used beyond manufacturer-specified lifetime.