Use of The FreeStyle NavigatorTM
Continuous Glucose Monitoring
System in Children on Glarginebased Multiple Daily Injection
Therapy
Stuart Weinzimer1, Dongyuan Xing2, Michael Tansey3,
Rosanna Fiallo-Scharer4, Nelly Mauras5, Tim Wysocki5, Roy
Beck2, William Tamborlane1, Katrina Ruedy2, Darrell
Wilson6, and the Diabetes Research in Children Network
(DirecNet) Study Group
1New Haven, CT; 2 Tampa, FL; 3Iowa City, IA; 4Denver, CO;
5Jacksonville,FL; 6Stanford, CA
Abstract
Introduction:
Real-time continuous glucose monitoring (CGM) can potentially
revolutionize the treatment of type 1 diabetes (T1D) in children. The Diabetes
Research in Children Network previously showed that pump-treated youth with T1D
using the FreeStyle Navigator lowered HbA1c and increased time spent in target range.
We hypothesized that the use of multiple daily injection (MDI) regimens, which offer
less flexibility than pumps, may limit the effectiveness of CGM to improve glycemic
control. Our objective was to determine whether youth utilizing glargine-based MDI
would benefit from daily use of the Navigator.
Methods: Following use of a masked Navigator for 4-7d to characterize baseline
glycemic control, 27 subjects (mean age 11.0  3.9y, mean diabetes duration 4.0 
3.1y) with T1D using basal-bolus MDI therapy with glargine were asked to use the
Navigator daily for 26 wks.
Results: 23 subjects completed both the 13- and 26-week visits. Sensor use
decreased slightly from median 121 hours per week at weeks 1-4 to 101 at weeks 913 (p=0.07), and continued to decline to 48 by weeks 22-26 (p<0.001 c/w wks 1-4).
Mean A1c decreased from baseline to 13 weeks (7.9  1.0% to 7.3  0.9%, p=0.004),
but rose again by 26 weeks (7.6  1.2%, p=0.17 from baseline). Subjects and parents
reported overall high levels of satisfaction with the Navigator, and subjects showed
improved quality of life with the Navigator.
Conclusions: Real-time CGM with the Navigator is feasible and tolerable in pediatric
patients using basal-bolus MDI and associated with reduced HbA1c and improved
quality of life over a 3 month period. Future pediatric trials of CGM should include both
MDI- and pump-treated patients and should concentrate on obstacles to continued
sensor use.
Background
•
Real-time continuous glucose monitoring devices (CGM)
are a potentially powerful tool in the management of
type 1 diabetes (T1D)
•
For successful adoption into clinical practice, they must
be accurate, comfortable to wear, and easy to use,
particularly in children
•
Previous studies of CGM in children have focused
primarily on children utilizing insulin pump therapy; it is
unknown whether this type of technology will be
tolerated and effective in children using intensive
multiple injection regimens, who may be unaccustomed
or unwilling to wear and/or use continuous devices
Study Aim
• The purpose of this pilot study was to
examine the effectiveness and tolerability
of a continuous glucose monitor (Abbott
Navigator) in children with type 1 diabetes
using intensive glargine-based multiple
daily injection (MDI) regimens
Research Design & Methods
•
27 children with T1D (4-17 yr old) using glargine-based
MDI wore the Navigator as an outpatient for 1 week but
were blinded to sensor data
•
Subjects then wore the Navigator (unblinded) as an
outpatient for 13 weeks
•
Devices were downloaded weekly to subjects’ home
computers and subjects were contacted frequently (q14wk) in order to monitor Navigator use
•
Questionnaires were completed at baseline and 13 weeks
•
Outcome measures included: glycemic control, glucose
variability, and tolerability (as assessed by questionnaire
scores)
Study Subjects
N
27 (23 completed)
Age
11.0 ± 3.9 yr
Female
14 (52%)
Caucasian
25 (93%)
Mean HbA1c
7.9 ± 1.0%
Mean T1D duration
4.0 ± 3.1 yr
MDI Regimen
Glargine + RAIA*
Glargine + RAIA* + NPH
Glargine + RAIA* + Reg
21 (78%)
5 (16%)
1 ( 4%)
* RAIA = Rapid-Acting Insulin Analog (Aspart or Lispro)
FreeStyle Navigator™ Continuous Glucose
Monitoring System
•
Measures interstitial glucose levels
•
Requires calibration using
fingerstick blood glucose at 10, 12,
24 and 72 hours after insertion
•
After a 10-hr warm-up, provides
glucose readings every 60 seconds
for up to 120 hours
•
Operating range 20 - 500 mg/dL
•
Displays a trend arrow indicating
glucose rate of change
•
Alarms for actual or impending
high or low glucose levels
Results – Glycemic Control
9.5
Baseline A1c > 7.5%
Baseline A1c ≤ 7.5%
9.0
HbA1c (%)
8.5
*
8.0
7.5
7.0
**
6.5
* p = 0.02
** p = 0.03
6.0
5.5
Baseline
Week 7
Week 13
The p-values shown were for comparisons of 9-13 wk vs. baseline.
Percentage sensor Glucose Values
In Target Range (71-180 mg/dL)
Results – Glycemic Targets
90%
Baseline A1c > 7.5%
80%
Baseline A1c ≤ 7.5%
70%
60%
50%
40%
30%
p = 0.68
p = 0.36
20%
Baseline
Wks 1-4
Wks 5-8
Wks 9-13
The p-values shown were for comparisons of 9-13 wk vs. baseline.
Questionnaires
Baseline
13 Weeks
Patients **
31 ± 10
31 ± 8
Parents
41 ± 10
41 ± 10
Patients **
31 ± 11
26 ± 12
Parents
37 ± 11
37 ± 14
Hypoglycemia Fear *
PedsQL †
CGM Satisfaction §
Patients **
3.5 ± 0.5
Parents
3.8 ± 0.4
* Lower score denotes less fear (possible range 15-75)
† Lower score denotes higher quality of life (possible range 0-112)
** completed by subjects ≥ 9 years of age
§ Higher score denotes greater satisfaction (possible range 1-5)
Results – Tolerability
Hours of sensor wear
200
Hours of glucose readings
Navigator Use (hours/week)
160
120
80
40
p = 0.25
p = 0.12
0
Baseline
Wks 1-4
Wks 5-8
Wks 9-13
Dots denote mean values and boxes denote median, 25th and 75th percentiles.
The p-values shown were for comparisons of 9-13 wk vs. 1-4 wk.
Results – Hypoglycemia
Percentage sensor Glucose Values
Below Target Range (< 70 mg/dL)
14%
12%
Baseline A1c > 7.5%
Baseline A1c ≤ 7.5%
10%
8%
6%
4%
2%
0%
p = 0.47
p = 0.61
Baseline Wks 1-4
Wks 5-8 Wks 9-13
The p-values shown were for comparisons of 9-13 wk vs. baseline.
Results – Glucose Variability
180
Baseline A1c > 7.5%
Mean Amplitude of Glycemic
Excursion (MAGE, mg/dL)
Baseline A1c ≤ 7.5%
160
*
140
120
100
* p = 0.004
p = 0.17
80
Baseline
Wks 1-4
Wks 5-8
Wks 9-13
The p-values shown were for comparisons of 9-13 wk vs. baseline.
Conclusions
•
Use of the Navigator CGM was associated with an
improvement in glycemic control without an
accompanying rise in hypoglycemia
•
Glycemic variability decreased with use of the
Navigator
•
Subjects and parents reported high overall
satisfaction with the Navigator and did not
demonstrate deterioration in quality of life during 3month use
•
CGM are tolerable and effective in children using MDI
regimens