Comparison of Glucose Monitoring Methods during Steady-State Exercise in Women

Abstract

Data from Continuous Glucose Monitoring (CGM) systems may help improve overall daily glycemia; however, the accuracy of CGM during exercise remains questionable. The objective of this single group experimental study was to compare CGM-estimated values to venous plasma glucose (VPG) and capillary plasma glucose (CPG) during steady-state exercise. Twelve recreationally active females without diabetes (aged 21.8 ± 2.4 years), from Central Washington University completed the study. CGM is used by individuals with diabetes, however the purpose of this study was to first validate the use of this device during exercise for anyone. Data were collected between November 2009 and April 2010. Participants performed two identical 45-min steady-state cycling trials (~60% Pmax) on non-consecutive days. Glucose concentrations (CGM-estimated, VPG, and CPG values) were measured every 5 min. Two carbohydrate gel supplements along with 360 mL of water were consumed 15 min into exercise. A product-moment correlation was used to assess the relationship and a Bland-Altman analysis determined error between the three glucose measurement methods. It was found that the CGM system overestimated mean VPG (mean absolute difference 17.4 mg/dL (0.97 mmol/L)) and mean CPG (mean absolute difference 15.5 mg/dL (0.86 mmol/L)). Bland-Altman analysis displayed wide limits of agreement (95% confidence interval) of 44.3 mg/dL (2.46 mmol/L) (VPG compared with CGM) and 41.2 mg/dL (2.29 mmol/L) (CPG compared with CGM). Results from the current study support that data from CGM did not meet accuracy standards from the 15197 International Organization for Standardization (ISO).

Interstitial Glucose and Physical Exercise in Type 1 Diabetes: Integrative Physiology, Technology, and the Gap In-Between

“…Unfortunately, in this trial, glucose concentrations were not classified for hypo-, eu-, and hyperglycemia during exercise. Disagreements in absolute glucose values during exercise between different compartments were found in healthy individuals [ 62 ] and in patients with type 1 diabetes [ 63 , 64 , 65 ]. Interstitial glucose concentrations measured via the SEVEN ® PLUS CGM (Dexcom, San Diego, CA, USA) system during exercise under euglycemic conditions are higher compared to capillary (finger sticks) and venous blood, and the capillary blood levels seem to be higher than the venous blood levels [ 62 ].…”

“…Disagreements in absolute glucose values during exercise between different compartments were found in healthy individuals [ 62 ] and in patients with type 1 diabetes [ 63 , 64 , 65 ]. Interstitial glucose concentrations measured via the SEVEN ® PLUS CGM (Dexcom, San Diego, CA, USA) system during exercise under euglycemic conditions are higher compared to capillary (finger sticks) and venous blood, and the capillary blood levels seem to be higher than the venous blood levels [ 62 ]. In patients with type 1 diabetes performing high-intensity interval exercise and continuous exercise, no clear trend was found in comparing the capillary blood glucose concentration (earlobe) and interstitial glucose concentration when using the Guardian REAL-time system and the Enlite sensor (Medtronic MiniMed, Inc., Northridge, CA, USA) (no classification for glycemic ranges was performed) [ 63 ].…”

Accuracy of continuous glucose monitoring during differing exercise conditions

“…Real-time use of continuous glucose monitoring (CGM) has recently emerged as a novel tool to improve glycemic control in patients with type 1 diabetes mellitus (T1DM) (1). While CGM is generally considered a reliable tool for diabetes management during resting conditions, the reliability in the setting of physical exercise remains controversial (2,3). Of importance, recent studies support the concept that CGM accurately reflects glucose changes even during the dynamic state of exercise (4).…”

Key Points from the Updated Guidelines on Exercise and Diabetes

“…They are able to provide blood glucose trends, which can potentially assist the user in preventing hypoglycemia or treating it sooner ( 60 – 63 ). Some issues with CGM use during activity remain, however, as stated in the PS ( 1 ): inadequate accuracy ( 64 ), sensor filament breakage ( 62 , 63 ), inability to calibrate ( 61 ) time lags between the change in blood glucose and its detection by CGM ( 65 ), and variations in sensor performance ( 66 – 68 ). CGM devices are currently being paired with insulin pumps into closed-loop systems run by algorithms.…”