title: Influence of time point of calibration on accuracy of continuous glucose monitoring in individuals with type 1 diabetes.
abstract: OBJECTIVE
  Data on the influence of calibration on accuracy of continuous glucose monitoring (CGM) are scarce. The aim of the present study was to investigate whether the time point of calibration has an influence on sensor accuracy and whether this effect differs according to glycemic level.
  
  
  METHODS
  Two CGM sensors were inserted simultaneously in the abdomen on either side of 20 individuals with type 1 diabetes. One sensor was calibrated predominantly using preprandial glucose (calibration(PRE)). The other sensor was calibrated predominantly using postprandial glucose (calibration(POST)). At minimum three additional glucose values per day were obtained for analysis of accuracy. Sensor readings were divided into four categories according to the glycemic range of the reference values (low, ≤4 mmol/L; euglycemic, 4.1-7 mmol/L; hyperglycemic I, 7.1-14 mmol/L; and hyperglycemic II, >14 mmol/L).
  
  
  RESULTS
  The overall mean±SEM absolute relative difference (MARD) between capillary reference values and sensor readings was 18.3±0.8% for calibration(PRE) and 21.9±1.2% for calibration(POST) (P<0.001). MARD according to glycemic range was 47.4±6.5% (low), 17.4±1.3% (euglycemic), 15.0±0.8% (hyperglycemic I), and 17.7±1.9% (hyperglycemic II) for calibration(PRE) and 67.5±9.5% (low), 24.2±1.8% (euglycemic), 15.5±0.9% (hyperglycemic I), and 15.3±1.9% (hyperglycemic II) for calibration(POST). In the low and euglycemic ranges MARD was significantly lower in calibration(PRE) compared with calibration(POST) (P=0.007 and P<0.001, respectively).
  
  
  CONCLUSIONS
  Sensor calibration predominantly based on preprandial glucose resulted in a significantly higher overall sensor accuracy compared with a predominantly postprandial calibration. The difference was most pronounced in the hypo- and euglycemic reference range, whereas both calibration patterns were comparable in the hyperglycemic range.
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zueger
authors.forename: Peter
authors.initials: P
authors.lastname: Diem
authors.forename: Stavroula
authors.initials: S
authors.lastname: Mougiakakou
authors.forename: Christoph
authors.initials: C
authors.lastname: Stettler
mesh_terms: D000328:Adult; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D001786:Blood Glucose / Q000378:metabolism*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation* / Q000379:methods; D002138:Calibration; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000097:blood*; D007003:Hypoglycemia / Q000097:blood*; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007332:Insulin Infusion Systems; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D011446:Prospective Studies; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents