title: Assessing the Accuracy of Continuous Glucose Monitoring (CGM) Calibrated With Capillary Values Using Capillary or Venous Glucose Levels as a Reference.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.affiliation: Department of Medicine, NU Hospital Group, Uddevalla, Sweden.
authors.forename: Mervi
authors.initials: M
authors.lastname: Andelin
authors.affiliation: Department of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Jort
authors.initials: J
authors.lastname: Kropff
authors.affiliation: Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Viktorija
authors.initials: V
authors.lastname: Matuleviciene
authors.affiliation: Department of Anaesthesiology, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Joseph
authors.affiliation: Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Stig
authors.initials: S
authors.lastname: Attvall
authors.affiliation: Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Sweden.
authors.forename: Elvar
authors.initials: E
authors.lastname: Theodorsson
authors.affiliation: University of Washington, Seattle, WA, USA.
authors.forename: Irl B
authors.initials: IB
authors.lastname: Hirsch
authors.affiliation: Statistiska Konsultgruppen, Gothenburg, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Imberg
authors.affiliation: Department of Medicine, NU Hospital Group, Uddevalla, Sweden.
authors.forename: Sofia
authors.initials: S
authors.lastname: Dahlqvist
authors.affiliation: Diabetes Research Institute, Mills-Peninsula Health Services, San Mateo, CA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Klonoff
authors.affiliation: Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Börje
authors.initials: B
authors.lastname: Haraldsson
authors.affiliation: Department of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.
authors.forename: J Hans
authors.initials: JH
authors.lastname: DeVries
authors.affiliation: Department of Medicine, NU Hospital Group, Uddevalla, Sweden Institute of Medicine, University of Gothenburg, Gothenburg, Sweden lind.marcus@telia.com.
authors.forename: Marcus
authors.initials: M
authors.lastname: Lind
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000592:standards*; D002138:Calibration; D002196:Capillaries; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D014680:Veins; D055815:Young Adult
chemical_list: D001786:Blood Glucose
keywords: accuracy; calibration; capillary; continuous glucose monitoring (CGM); type 1 diabetes; venous
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