Analysis of Time Lags and Other Sources of Error of the DexCom SEVEN Continuous Glucose Monitor

Abstract

For this sensor, the assumption of substantial time lag and its suggested effects may be incorrect. The main source of error is the calibration process.

Performance Evaluation of Three Continuous Glucose Monitoring Systems: Comparison of Six Sensors Per Subject in Parallel

“…Thus, CGM systems still have lower accuracy than devices for SMBG; however, when an SMBG device is used for calibration, as in the study presented here, its accuracy (precision and trueness) directly affects the CGM's accuracy. 10 The study setting was designed as a compromise between prerequisites of POCT05-A, a Clinical and Laboratory Standards Institute guideline providing recommendations for evaluating performance of CGM systems, and parallel use of sensors in an in-house setting similar to daily life using induced excursions at the beginning of sensor use and calibration phase and at a later time in sensor use. Only one study claimed to follow POCT05-A recommendations in design and evaluation.…”

“…13 The study presented here is, to the best knowledge of the authors, the first to use two sensors of three different CGM systems in parallel for the respective entire lifetime of the sensor, thus allowing the evaluation of accuracy (with regard to BG measurements) as well as sensor-to-sensor precision between different sensors of one type of CGM system. 23 In other studies in which more than one sensor was used per subject, only one type of CGM system was used, 3,4,6,[8][9][10][11]15 and in studies that compared multiple CGM systems, only one sensor per subject was used. 2,7,12,19 In this study, both aspects were combined, thus allowing an evaluation in which groups of six sensors (i.e., two sensors of each of three CGM systems in one individual subject) follow identical glycemic excursions.…”

“…In 2008, the Clinical and Laboratory Standards Institute published POCT05-A, which provides recommendations for study design and parameters of interest in the performance evaluation of CGM systems. 1 Multiple studies investigating CGM systems were published over the years; [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] only one claimed to use procedures recommended in POCT05-A. 13 A comparison of these studies, however, is difficult due to variations in subject groups 11 and study design, including use of different devices for calibration of CGM systems and for reference measurements, either overall or for different study phases.…”

“…13 A comparison of these studies, however, is difficult due to variations in subject groups 11 and study design, including use of different devices for calibration of CGM systems and for reference measurements, either overall or for different study phases. [2][3][4][6][7][8][9][10]12,13,16,17 Given that comparability of different CGM systems is heavily influenced by these factors, it is thus improved when the different CGM systems are worn simultaneously by the same subjects under identical conditions (e.g., in head-to-head comparisons). There are studies in which different CGM systems were compared under such conditions, 2,7,12 but in these cases, only one sensor per CGM system was worn by the subjects.…”

Clinical Implications of Accuracy Measurements of Continuous Glucose Sensors

“…ROC has also been shown to impact MARD. 21,22 Additional factors that impact the calculation of MARD include the absolute number of data points, their distribution, and missing data points. 13 Calibration, for most devices, is required both initially and at subsequent intervals to compensate for sensor ''drift.''…”