title: Measurement delay associated with the Guardian RT continuous glucose monitoring system.
abstract: OBJECTIVE
  Using compartment modelling, we assessed the time delay between blood glucose and sensor glucose measured by the Guardian RT continuous glucose monitoring system in young subjects with Type 1 diabetes (T1D).
  
  
  METHODS
  Twelve children and adolescents with T1D treated by continuous subcutaneous insulin infusion (male/female 7/5; age 13.1 +/- 4.2 years; body mass index 21.9 +/- 4.3 kg/m(2); mean +/- sd) were studied over 19 h in a Clinical Research Facility. Guardian RT was calibrated every 6 h and sensor glucose measured every 5 min. Reference blood glucose was measured every 15 min using a YSI 2300 STAT Plus Analyser. A population compartment model of sensor glucose-blood glucose kinetics was adopted to estimate the time delay, the calibration scale and the calibration shift.
  
  
  RESULTS
  The population median of the time delay was 15.8 (interquartile range 15.2, 16.5) min, which was corroborated by correlation analysis between blood glucose and 15-min delayed sensor glucose. The delay has a relatively low intersubject variability, with 95% of individuals predicted to have delays between 10.4 and 24.3 min. Population medians (interquartile range) for the scale and shift are 0.800 (0.777, 0.823) (unitless) and 1.66 (1.47, 1.84) mmol/l, respectively.
  
  
  CONCLUSIONS
  In young subjects with T1D, the total time delay associated with the Guardian RT system was approximately 15 min. This is twice that expected on physiological grounds, suggesting a 5- to 10-min delay because of data processing. Delays above 25 min are rarely to be observed.
authors.affiliation: MRC Biostatistics Unit, Institute of Public Health, University of Cambridge, Cambridge, UK. chen.wei@mrc-bsu.cam.ac.uk
authors.forename: C
authors.initials: C
authors.lastname: Wei
authors.forename: D J
authors.initials: DJ
authors.lastname: Lunn
authors.forename: C L
authors.initials: CL
authors.lastname: Acerini
authors.forename: J M
authors.initials: JM
authors.lastname: Allen
authors.forename: A M
authors.initials: AM
authors.lastname: Larsen
authors.forename: M E
authors.initials: ME
authors.lastname: Wilinska
authors.forename: D B
authors.initials: DB
authors.lastname: Dunger
authors.forename: R
authors.initials: R
authors.lastname: Hovorka
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation* / Q000592:standards; D015992:Body Mass Index; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D001786:Blood Glucose