title: Accuracy of Continuous Glucose Monitoring Measurements in Normo-Glycemic Individuals.
abstract: BACKGROUND
  The validity of continuous glucose monitoring (CGM) is well established in diabetic patients. CGM is also increasingly used for research purposes in normo-glycemic individuals, but the CGM validity in such individuals is unknown. We studied the accuracy of CGM measurements in normo-glycemic individuals by comparing CGM-derived versus venous blood-derived glucose levels and measures of glycemia and glycemic variability.
  
  
  METHODS
  In 34 healthy participants (mean age 65.7 years), glucose was simultaneously measured every 10 minutes, via both an Enlite® CGM sensor, and in venous blood sampled over a 24-hour period. Validity of CGM-derived individual glucose measurements, calculated measures of glycemia over daytime (09:00h-23:00h) and nighttime (23:00h-09:00h), and calculated measures of glycemic variability (e.g. 24h standard deviation [SD]) were assessed by Pearson correlation coefficients, mean absolute relative difference (MARD) and paired t-tests.
  
  
  RESULTS
  The median correlation coefficient between CGM and venous glucose measurements per participant was 0.68 (interquartile range: 0.40-0.78), and the MARD was 17.6% (SD = 17%). Compared with venous sampling, the calculated measure of glycemia during daytime was 0.22 mmol/L higher when derived from CGM, but no difference was observed during nighttime. Most measures of glycemic variability were lower with CGM than with venous blood sampling (e.g., 24h SD: 1.07 with CGM and 1.26 with venous blood; p-value = 0.004).
  
  
  CONCLUSIONS
  In normo-glycemic individuals, CGM-derived glucose measurements had good agreement with venous glucose levels. However, the measure of glycemia was higher during the day and most measures of glycemic variability were lower when derived from CGM.
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Abimbola A
authors.initials: AA
authors.lastname: Akintola
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Raymond
authors.initials: R
authors.lastname: Noordam
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Steffy W
authors.initials: SW
authors.lastname: Jansen
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Anton J
authors.initials: AJ
authors.lastname: de Craen
authors.affiliation: Department of Clinical Chemistry, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Bart E
authors.initials: BE
authors.lastname: Ballieux
authors.affiliation: Department of Clinical Chemistry, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Christa M
authors.initials: CM
authors.lastname: Cobbaert
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Mooijaart
authors.affiliation: Department of Endocrinology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Hanno
authors.initials: H
authors.lastname: Pijl
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands; Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Rudi G
authors.initials: RG
authors.lastname: Westendorp
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Diana
authors.initials: D
authors.lastname: van Heemst
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring; D015992:Body Mass Index; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D006454:Hemoglobins