1. The Physiological Variations of Plasma Glucose Concentrations in Healthy, Non-Diabetic Children: Use of Continuous Glucose Sensors Nelly Mauras, Roy Beck, Katrina Ruedy, Andrea Booth, Stuart Weinzimer, and the Diabetes Research in Children Network (DirecNet) Study Group.

2. Clinical Centers
Barbara Davis Center for Childhood Diabetes, Denver, CO
Nemours Children’s Clinic, Jacksonville, FL
Stanford University Medical Center, Stanford, CA
University of Iowa, Iowa City, IA
Yale University Medical Center, New Haven, CT
Coordinating Center
Jaeb Center for Health Research, Tampa, FL

3. Background
Characterization of the diurnal variations in plasma glucose in
normal children is critical for the interpretation of glucose values
using continuous glucose sensors in pathological states, such as
diabetes and hypoglycemic conditions.
Preliminary reports and anecdotal data suggest that non-diabetic
children have low sensor glucose levels, especially at night
(Weinzimer SA, et al, Diabet Technol Ther 2003).

4. Objective To determine the accuracy of 2 glucose sensors, the
Continuous Glucose Monitoring System (CGMS -
Medtronics/Minimed) and the Glucowatch® G2TM Biographer (GW2B-Cygnus) in healthy, non diabetic children while examining the 24h pattern of glucose concentrations.

5. Inclusion Criteria healthy boys and girls ages 7 to 17 years
normal HbA1C
no first degree relatives with diabetes
BMI between 10th and 90th percentile
normal Hematocrit
no skin abnormalities contraindicating sensor use

6. Procedures All patients were admitted to each center’s CRC
An iv catheter was placed after numbing skin for
reference blood glucose determinations every hour
during the day (7AM to 9PM) and every 1/2 hour
overnight (9:30PM to 6:30AM).

7. Glucowatch Biographer
Measures blood
glucose from interstitial
fluid via reverse
iontophoresis.

8. CGMS Measures blood glucose via
a glucose oxidase based electrochemical
sensor.
CGMS

11. GW2B Accuracy Summary Statistics
Total :00PM-6:00AM :30AM -10:30PM
Paired data points
Absolute difference (median)
(mg/dl) (25, 75th percentiles) (6,23) (6,24) (7,21)
%Values within 10 mg/dl % % %
%Values within 20 mg/dl % % %

12. CGMS Accuracy Summary Statistics
Total :00PM-6:00AM :30AM -10:30PM
Paired data points
Absolute difference (median)
(mg/dl) (25, 75th percentiles) (8,29) (8,29) (7,29)
%Values within 10 mg/dl % % %
%Values within 20 mg/dl % % %

13. Low glucose readings by sensors
GW2B CGMS
108
139
Values <60 mg/dl
7/108
1/139
Isolated readings
Coincided with reference
glucose
33/108
14/139
Paired value had reference
glucose >70 mg/dl
33/33
14/14

14. Glucose values measured by reference lab,
CGMS and GW2B sensors

15. Glucose values measured by reference lab,
CGMS and GW2B sensors

16. Mean and range serum glucose concentrations (mg/dL)
measured by reference lab in healthy children (N=15)
Time of Day
Glucose (mg/dL)

17. Summary
In healthy non-diabetic children wearing continuous glucose sensors:
the median absolute difference in glucose concentrations
between the GW2B and reference glucose concentrations
is 13 mg/dl, with 40% of values within 10mg/dl of the
reference value
for CGMS the median absolute difference is 17 mg/dl with
34% of values within 10mg/dl of the laboratory reference.

18. Conclusions Our data support that:
1) neither the GW2B nor CGMS is accurate enough to
provide normative glycemia profiles for non-diabetic children
2) previous reports of low sensor glucose values in non-diabetic
children may represent inaccurate glucose measurements
3) serum glucose concentrations in non-diabetic children are
tightly controlled.