Test-retest reliability of a continuous glucose monitoring system in individuals with type 2 diabetes

Diabetes Technol Ther. 2014 Aug;16(8):491-8. doi: 10.1089/dia.2013.0355. Epub 2014 May 9.


Aims: 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).

Subjects and 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosensing Techniques
  • Blood Glucose / metabolism*
  • Calorimetry / methods*
  • Diabetes Mellitus, Type 2 / blood*
  • Diabetes Mellitus, Type 2 / drug therapy
  • Diabetes Mellitus, Type 2 / physiopathology
  • Energy Metabolism
  • Exercise
  • Female
  • Glucose Tolerance Test
  • Glycated Hemoglobin A / metabolism*
  • Glycemic Index
  • Humans
  • Male
  • Meals
  • Middle Aged
  • Monitoring, Physiologic*
  • Quality Assurance, Health Care
  • Reference Values
  • Reproducibility of Results


  • Blood Glucose
  • Glycated Hemoglobin A
  • hemoglobin A1c protein, human