title: Test-retest reliability of a continuous glucose monitoring system in individuals with type 2 diabetes.
abstract: OBJECTIVE
  This study determined the test-retest reliability of a continuous glucose monitoring system (CGMS) (iPro™2; Medtronic, Northridge, CA) under standardized conditions in individuals with type 2 diabetes (T2D).
  
  
  METHODS
  Fourteen individuals with T2D spent two nonconsecutive days in a calorimetry unit. On both days, meals, medication, and exercise were standardized. Glucose concentrations were measured continuously by CGMS, from which daily mean glucose concentration (GLU(mean)), time spent in hyperglycemia (t(>10.0 mmol/L)), and meal, exercise, and nocturnal mean glucose concentrations, as well as glycemic variability (SD(w), percentage coefficient of variation [%cv(w)], mean amplitude of glycemic excursions [MAGEc, MAGE(ave), and MAGE(abs.gos)], and continuous overlapping net glycemic action [CONGA(n)]) were estimated. Absolute and relative reliabilities were investigated using coefficient of variation (CV) and intraclass correlation, respectively.
  
  
  RESULTS
  Relative reliability ranged from 0.77 to 0.95 (P<0.05) for GLU(mean) and meal, exercise, and nocturnal glycemia with CV ranging from 3.9% to 11.7%. Despite significant relative reliability (R=0.93; P<0.01), t(>10.0 mmol/L) showed larger CV (54.7%). Among the different glycemic variability measures, a significant between-day difference was observed in MAGEc, MAGE(ave), CONGA6, and CONGA12. The remaining measures (i.e., SD(w), %cv(w), MAGE(abs.gos), and CONGA1-4) indicated no between-day differences and significant relative reliability.
  
  
  CONCLUSIONS
  In individuals with T2D, CGMS-estimated glycemic profiles were characterized by high relative and absolute reliability for both daily and shorter-term measurements as represented by GLUmean and meal, exercise, and nocturnal glycemia. Among the different methods to calculate glycemic variability, our results showed SD(w), %cv(w), MAGE(abs.gos), and CONGAn with n ≤ 4 were reliable measures. These results suggest the usefulness of CGMS in clinical trials utilizing repeated measured.
authors.affiliation: 1 Faculty of Physical Education & Recreation, University of Alberta , Edmonton, Alberta, Canada .
authors.forename: Tasuku
authors.initials: T
authors.lastname: Terada
authors.forename: Sarah
authors.initials: S
authors.lastname: Loehr
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Guigard
authors.forename: Linda J
authors.initials: LJ
authors.lastname: McCargar
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Bell
authors.forename: Peter
authors.initials: P
authors.lastname: Senior
authors.forename: Normand G
authors.initials: NG
authors.lastname: Boulé
mesh_terms: D015374:Biosensing Techniques; D001786:Blood Glucose / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism*; D038321:Glycemic Index; D006801:Humans; D008297:Male; D062407:Meals; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011785:Quality Assurance, Health Care; D012016:Reference Values; D015203:Reproducibility of Results
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human