title: Accuracy assessment of online glucose monitoring by a subcutaneous enzymatic glucose sensor during exercise in patients with type 1 diabetes treated by continuous subcutaneous insulin infusion.
abstract: OBJECTIVE
  Online continuous glucose monitoring (CGM) during physical exercise would be highly useful in patients with insulin-treated diabetes. For this reason, this study assessed whether such a goal could be reached with a subcutaneous 'needle-type' enzymatic sensor.
  
  
  METHODS
  Ten patients (five women/five men), aged 51 ± 12 years, with type 1 diabetes for 24 ± 11 years treated by continuous subcutaneous insulin infusion (CSII) for more than 1 year (HbA1c: 7.5 ± 0.8%) performed a 30-min bout of exercise at a constant high-intensity load (15% above their individual ventilatory threshold) on a cycle ergometer. All patients wore a subcutaneous 'needle-type' enzymatic glucose sensor linked to a portable monitor (Guardian(®) RT, Medtronic-MiniMed, Northridge, CA, USA) that had been inserted the previous evening. Sensor calibration was performed against capillary blood glucose immediately before the exercise. CGM values were recorded every 5 min from T(-10) to T(+30), then every 10 min during the recovery period from T(+30) to T(+90). These recorded values were compared with blood glucose assays performed on simultaneously collected venous samples.
  
  
  RESULTS
  Sensor functioning and tolerability raised no problems except for one sensor that could not be adequately calibrated. Data from this patient were excluded from the data analysis. An average blood glucose decrease of 63 ± 63 mg/dL (3.5 ± 3.5 mmol/L) (median decrease: 58 mg/dL [3.22 mmol/L]; range: -3 mg/dL [0.16 mmol/L] to 178 mg/dL [9.8 mmol/L]) occurred during exercise bouts, while CGM values decreased by 38 ± 49 mg/dL (2.11 ± 2.72 mmol/L) (median: 32 mg/dL [1.7 mmmol/L]; range: -15 mg/dL [0.83 mmol/L] to 58 mg/dL [3.22 mmol/L]). Cumulative paired glucose values (n = 135) could be analyzed. The correlation factor between CGM and blood glucose values was 0.957 with an intercept of 0.275. The mean difference between paired values according to Bland-Altman analysis was 10 ± 31 mg/dL (0.56 ± 1.72 mmol/L). Clarke error grid analysis showed 91% of paired points in A and B zones, while 0%, 9% and 0% of paired points were in the C, D and E zones, respectively.
  
  
  CONCLUSIONS
  Blood glucose changes during intensive physical-exercise bouts performed by CSII-treated type 1 diabetes patients can be estimated with acceptable clinical accuracy by online CGM.
authors.affiliation: Division of Diabetes, Nutrition and Metabolic Disorders, CHU Liège, University of Liège, Liège, Belgium. regis.radermecker@chu.ulg.ac.be
authors.forename: R-P
authors.initials: RP
authors.lastname: Radermecker
authors.forename: C
authors.initials: C
authors.lastname: Fayolle
authors.forename: J-F
authors.initials: JF
authors.lastname: Brun
authors.forename: J
authors.initials: J
authors.lastname: Bringer
authors.forename: E
authors.initials: E
authors.lastname: Renard
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000379:methods* / Q000592:standards; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy* / Q000453:epidemiology; D015444:Exercise; D005260:Female; D006801:Humans; D055104:Infusions, Subcutaneous; D007328:Insulin / Q000008:administration & dosage*; D007332:Insulin Infusion Systems; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods
chemical_list: D001786:Blood Glucose; D007328:Insulin