The Accuracy and Precision of the Continuously Stored Data from Flash Glucose Monitoring System in Type 2 Diabetes Patients during Standard Meal Tolerance Test

Abstract

Background. The purpose of this study was to investigate the accuracy of the continuously stored data from the Abbott FreeStyle Libre flash glucose monitoring (FGM) system in Chinese diabetes patients during standard meal tests when glucose concentrations were rapidly changing. Subjects and Methods. Interstitial glucose levels were monitored for 14 days in 26 insulin-treated patients with type 2 diabetes using the FGM system. Standard meal tests were conducted to induce large glucose swings. Venous blood glucose (VBG) was tested at 0, 30, 60, and 120 min after standard meal tests in one middle day of the first and second weeks, respectively. The corresponding sensor glucose values were obtained from interpolating continuously stored data points. Assessment of accuracy was according to recent consensus recommendations with median absolute relative difference (MARD) and Clarke and Parkes error grid analysis (CEG and PEG). Results. Among 208 paired sensor-reference values, 100% were falling within zones A and B of the Clarke and Parkes error grid analysis. The overall MARD was 10.7% (SD, 7.8%). Weighted least squares regression analysis resulted in high agreement between the FGM sensor glucose and VBG readings. The overall MTT results showed that FGM was lower than actual VBG, with MAD of 22.1 mg/dL (1.2 mmol/L). At VBG rates of change of -1 to 0, 0 to 1, 1 to 2, and 2 to 3 mg/dl/min, MARD results were 11.4% (SD, 8.7%), 9.4% (SD, 6.5%), 9.9% (SD, 7.5%), and 9.5% (SD, 7.7%). At rapidly changing VBG concentrations (>3 mg/dl/min), MARD increased to 19.0%, which was significantly higher than slow changing BG groups. Conclusions. Continuously stored interstitial glucose measurements with the FGM system were found to be acceptable to evaluate VBG in terms of clinical decision during standard meal tests. The continuously stored data from the FGM system appeared to underestimate venous glucose and performed less well during rapid glucose changes.

Accuracy of Flash Glucose Monitoring During Postprandial Rest and Different Walking Conditions in Overweight or Obese Young Adults

“…Continuous glucose monitoring readings have been reported to be lower than PG (Yardley et al, 2013;Yan et al, 2020). Consistently, FGM readings were 0.8-1.2 mmol•L −1 lower than PG during postmeal sitting and walking conditions in the present study (Supplementary Table 1).…”

“…In the present study, the Bland-Altman method and the Clarke error grid analysis showed that the FGM values were clinically acceptable (Figures 3, 4). In previous studies, almost 100% of the value pairs fell within zones A and B of the Clarke error grid analysis (Bally et al, 2016;Moser et al, 2016;Biagi et al, 2018;Yan et al, 2020). This excellent, clinically acceptable accuracy proved that the CGM accuracy during postmeal resting and walking was high and was further verified using the Bland-Altman method and Pearson's correlation analysis.…”

“…A more recent meta-analysis (Fabra et al, 2021) compared the mean absolute relative difference (MARD) during exercise and rest, showing that exercise negatively affects CGM accuracy. Some studies have reported poor performance during rapid glucose changes after a meal (Yan et al, 2020) or during exercise (Biagi et al, 2018;Heden et al, 2018;Moser et al, 2019). One possible reason for this underestimation is the time delay between blood and interstitial fluid compartments.…”

Performance of the Intermittently Scanned Continuous Glucose Monitoring (isCGM) System during a High Oral Glucose Challenge in Adults with Type 1 Diabetes—A Prospective Secondary Outcome Analysis

“…Considering the low MARD found in our study, it can be concluded that isCGM tracks post-prandial glucose excursions accurately in situations of nutritionally induced rapid glucose changes. Although performed in people with type 2 diabetes, similar findings were found during standard meal tests, detailing that 100% of isCGM comparison points were falling within zones A and B of the Clarke and Parkes error grid analysis accompanied by a MARD of 10.7% [ 15 ]. However, in this study, it was also found that, during rapidly changing glucose concentrations, the MARD increased to 19.0%, which exceeds the number observed in our (very) high RCPG.…”

Glycopenia - induced sympathoadrenal activation in diabetes mellitus and uncontrolled arterial hypertension: an observational study

“…Therefore, the high rate of hypoglycemic episodes in Group 1 is unexpected. Although flash CGM technology was proven to be accurate in comparison to capillary-blood glucose tests [ 30 ], technical limitations include a period of 12 h after placing the senso when flash CGM readings are unreliable [ 31 ], inaccurate CGM values during rapid excursions of blood glucose [ 32 ] and during exercise [ 33 ]. Overall, the accuracy of flash CGM was shown to be slightly lower in the hypoglycemic range, though more hypoglycemic episodes were detected [ 34 ].…”