Calibration of the continuous glucose monitoring system for transient glucose monitoring.
BACKGROUND
Oral glucose tolerance testing (OGTT) remains the gold standard for diagnosis of diabetes and is used commonly in the research laboratory. The Medtronic MiniMed (North-ridge, CA) Continuous Glucose Monitoring System (CGMS Gold), developed for long-term monitoring of glycemic levels, could provide a convenient means for tracking OGTT results during research protocols; however, the sensor demonstrates glucose and time dependencies that preclude direct application of the company-provided conversion algorithm in the first 12-24 h after sensor insertion. Here, we propose an alternative conversion algorithm that permits utilization of the CGMS monitor for glucose monitoring during this time.


METHODS
Healthy female participants underwent CGMS monitoring during OGTT or fasting sessions in combination with finger-stick blood glucose measurements. Logarithmic transformations and multiple regression analysis were used to quantify the time and glucose dependence of the sensors.


RESULTS
Sensor performance, as characterized by sensitivity (ratio of sensor current to capillary blood glucose levels), was shown to vary logarithmically with glucose levels as well as time after sensor insertion. A conversion algorithm developed on the basis of these observations was tested on 17 subjects during OGTT. A mean absolute relative difference between capillary blood glucose and CGMS values of 11.6 +/- 6.5% for the new algorithm was seen, compared to 20.6 +/- 5.9% with the Medtronic Solutions version 3.0c algorithm.


CONCLUSIONS
Incorporation of the glucose and time dependence in CGMS sensor data yields an improved mean absolute difference between actual and estimated blood glucose values compared to the Medtronic-supplied algorithm in the immediate time period following sensor insertion.
Lesperance
Leann M
LM
Clinical Science and Engineering Research Center, Binghamton University, Binghamton, New York 13902-6000, USA. llespera@binghamton.edu
Spektor
Anna
A
McLeod
Kenneth J
KJ
D000328:Adult; D000465:Algorithms; D001786:Blood Glucose / Q000032:analysis*; D002138:Calibration; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001786:Blood Glucose