Mervi Andelin1, Jort Kropff2, Viktorija Matuleviciene3, Jeffrey I Joseph4, Stig Attvall3, Elvar Theodorsson5, Irl B Hirsch6, Henrik Imberg7, Sofia Dahlqvist1, David Klonoff8, Börje Haraldsson3, J Hans DeVries2, Marcus Lind9. 1. Department of Medicine, NU Hospital Group, Uddevalla, Sweden. 2. Department of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands. 3. Institute of Medicine, University of Gothenburg, Gothenburg, Sweden. 4. Department of Anaesthesiology, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA. 5. Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Sweden. 6. University of Washington, Seattle, WA, USA. 7. Statistiska Konsultgruppen, Gothenburg, Sweden. 8. Diabetes Research Institute, Mills-Peninsula Health Services, San Mateo, CA, USA. 9. Department of Medicine, NU Hospital Group, Uddevalla, Sweden Institute of Medicine, University of Gothenburg, Gothenburg, Sweden lind.marcus@telia.com.
Abstract
BACKGROUND: Using the standard venous reference for the evaluation of continuous glucose monitoring (CGM) systems could possibly negatively affect measured CGM accuracy since CGM are generally calibrated with capillary glucose and venous and capillary glucose concentrations differ. We therefore aimed to quantify the effect of using capillary versus venous glucose reference samples on estimated accuracy in capillary calibrated CGM. METHODS: We evaluated 41 individuals with type 1 diabetes mellitus (T1DM) using the Dexcom G4 CGM system over 6 days. Patients calibrated their CGM devices with capillary glucose by means of the HemoCue system. During 2 visits, capillary and venous samples were simultaneously measured by HemoCue and compared to concomitantly obtained CGM readings. The mean absolute relative difference (MARD) was calculated using capillary and venous reference samples. RESULTS: Venous glucose values were 0.83 mmol/L (15.0 mg/dl) lower than capillary values over all glycemic ranges, P < .0001. Below 4 mmol/l (72 mg/dl), the difference was 1.25 mmol/l (22.5 mg/dl), P = .0001, at 4-10 mmol/l (72-180 mg/dl), 0.67 mmol/l (12.0 mg/dl), P < .0001 and above 10 mmol/l (180 mg/dl), 0.95 mmol/l (17.1 mg/dl), P < .0001. MARD was 11.7% using capillary values as reference compared to 13.7% using venous samples, P = .037. Below 4 mmol/l (72 mg/dl) MARD was 16.6% and 31.8%, P = .048, at 4-10 mmol/l (72-180 mg/dl) 12.1% and 12.6%, P = .32, above 10 mmol/l (180 mg/dl) 8.7% and 9.2%, P = .82. CONCLUSION: Using capillary glucose concentrations as reference to evaluate the accuracy of CGM calibrated with capillary samples is associated with a lower MARD than using venous glucose as the reference. Capillary glucose concentrations were significantly higher than venous in all glycemic ranges.
BACKGROUND: Using the standard venous reference for the evaluation of continuous glucose monitoring (CGM) systems could possibly negatively affect measured CGM accuracy since CGM are generally calibrated with capillary glucose and venous and capillary glucose concentrations differ. We therefore aimed to quantify the effect of using capillary versus venous glucose reference samples on estimated accuracy in capillary calibrated CGM. METHODS: We evaluated 41 individuals with type 1 diabetes mellitus (T1DM) using the Dexcom G4 CGM system over 6 days. Patients calibrated their CGM devices with capillary glucose by means of the HemoCue system. During 2 visits, capillary and venous samples were simultaneously measured by HemoCue and compared to concomitantly obtained CGM readings. The mean absolute relative difference (MARD) was calculated using capillary and venous reference samples. RESULTS:Venous glucose values were 0.83 mmol/L (15.0 mg/dl) lower than capillary values over all glycemic ranges, P < .0001. Below 4 mmol/l (72 mg/dl), the difference was 1.25 mmol/l (22.5 mg/dl), P = .0001, at 4-10 mmol/l (72-180 mg/dl), 0.67 mmol/l (12.0 mg/dl), P < .0001 and above 10 mmol/l (180 mg/dl), 0.95 mmol/l (17.1 mg/dl), P < .0001. MARD was 11.7% using capillary values as reference compared to 13.7% using venous samples, P = .037. Below 4 mmol/l (72 mg/dl) MARD was 16.6% and 31.8%, P = .048, at 4-10 mmol/l (72-180 mg/dl) 12.1% and 12.6%, P = .32, above 10 mmol/l (180 mg/dl) 8.7% and 9.2%, P = .82. CONCLUSION: Using capillary glucose concentrations as reference to evaluate the accuracy of CGM calibrated with capillary samples is associated with a lower MARD than using venous glucose as the reference. Capillary glucose concentrations were significantly higher than venous in all glycemic ranges.
Authors: David M Nathan; Patricia A Cleary; Jye-Yu C Backlund; Saul M Genuth; John M Lachin; Trevor J Orchard; Philip Raskin; Bernard Zinman Journal: N Engl J Med Date: 2005-12-22 Impact factor: 91.245
Authors: J Kropff; D Bruttomesso; W Doll; A Farret; S Galasso; Y M Luijf; J K Mader; J Place; F Boscari; T R Pieber; E Renard; J H DeVries Journal: Diabetes Obes Metab Date: 2014-09-10 Impact factor: 6.577