The average age of the 30 subjects was 11.2 ± 4.1 years (range 4 to 17) and 40% were female. Mean duration of diabetes was 5.8 ± 3.0 years. Mean A1c was 7.1 ± 0.6%, with 15 of the subjects having an A1c ≤7.0% (mean age 11.1 years) and 15 having an A1c >7.0% (mean age 11.3 years). None of the subjects reported a severe episode of hypoglycemia in the 6 months prior to the study.
The 1, 3 and 7-week visits were completed by all 30 subjects. Two (7%) subjects (age 4 with baseline A1c of 6.8% and age 11 years with baseline A1c of 6.9%) dropped out of the study following the 7-week visit, one due to difficulty wearing the sensor and the other due to perceived insufficient accuracy. The remaining 28 subjects completed the 13-week visit. There were 19 unscheduled visits from 11 subjects due to problems/questions with the Navigator (N=12), skin reaction (N=3), to pick up study supplies (N=2), to review insulin dose guidelines for persistent hyperglycemia (N=1) or to download their insulin pump (N=1). Ninety-nine percent of the scheduled phone calls were completed.
During the first 4 weeks of unblinded sensor use, the sensor was worn an average of 149 ± 22 hours per week (out of a maximum of 168 hours in a week), with an average 120 ± 27 hours of glucose readings (out of a maximum of 148 hours per week accounting for the 10-hour warm-up period for each sensor). Navigator use decreased slightly throughout the study averaging 134 ± 37 hours of wear and 104 ± 39 hours of glucose values per week during weeks 9 to 13 (P=0.006 and 0.003, respectively). Seventeen (57%) of the 30 subjects averaged at least 6 days of Navigator use per week and only 2 subjects used the device for less than 4 days per week. Among 9 subjects who reported using the Navigator less than 7 days per week at the 13-week visit, reasons reported for lack of use included: too busy (N=4), skin irritation (N=1), trouble with calibration (N=1), lost receiver (N=1), ran out of sensors (N=1) and difficulty with adhesion and bleeding at insertion site (N=1).
The mean number of FreeStyle glucose meter measurements (excluding measurements made for calibration) declined steadily from 5.0 ± 2.0 per day during the first 4 weeks to 4.1 ± 2.5 per day during weeks 5 to 8 to 3.8 ± 2.2 per day during weeks 9 to 13 (p<0.001). During weeks 9 to 13, 29% of subjects averaged <2.0 meter measurements a day, 18% averaged 2.0 to <4.0 measurements a day, 39% averaged 4.0 to <6.0 measurements a day, and 14% averaged 6.0 or more measurements a day.
During the 13 weeks of the study, 626 sensors were used by the 30 subjects. Seventy-six (12%) of the 626 sensors never provided glucose data, either because of insertion problems, inability to calibrate, or other reason. Among the other 550 sensors, the median time from insertion to the last glucose value was 98 hours (interquartile range 58 to 120), with 52 (9%) functioning for <24 hours, 69 (13%) for 24 to <48h, 70 (13%) for 48 to <72 hours, 71 (13%) for 72 to <96 hours, and 288 (52%) for 96 to 120 hours. Thirty-two Navigator kits from 18 subjects were replaced during the study, 19 due to a broken receiver or transmitter and 13 due to the receiver and or transmitter not working properly.
Twenty-six of the 28 subjects completing the 13-week visit elected to continue use of the Navigator during the optional continuation phase. The reasons given for the two who declined were (1
) problems with calibrations and (2
) embarrassment caused by the frequent alarms in class and difficulties with the timing of the required calibrations.
For the 28 subjects completing the 13-week visit, A1c values dropped from 7.1 ± 0.6% at baseline to 6.8 ± 0.7% at 13 weeks (p=0.02, ). The change in A1c was 0.0 ± 0.4% for the 13 subjects whose baseline A1c was ≤7.0% (mean 6.6 ± 0.4%) whereas A1c levels decreased from 7.6 ± 0.4% to 7.0 ± 0.7% in the 15 subjects whose baseline A1c was >7.0%. Among the 15 subjects with baseline A1c >7.0%, a decrease of 0.5% or more from baseline to 13 weeks occurred in 9 (60%). Mean glucose concentration dropped and the percentage of sensor values in the target range of 71 to 180 mg/dL rose during the first 4 weeks and remained steady through weeks 9 to 13 (p=0.002 and p=0.01 respectively for change from baseline to 9-13 weeks). Glycemic variation also decreased during the study period ().
Major Outcomes Summary Table (mean ± SD or %)
The percentage of Navigator values ≤70 mg/dL was 4.5% at baseline, 5.1% during weeks 1 to 4 and 5.5% during weeks 9 to 13 (p=0.07 comparing baseline to 9-13 weeks), with a similar but less pronounced trend in the percentage of values ≤60 mg/dL (). The percentage of values ≤70 mg/dL was 2.5% at baseline and 5.0% at 13 weeks for subjects whose baseline A1c was >7.0% (p=0.06), and 6.6% and 6.1% respectively for subjects with baseline A1c ≤7.0% (P=0.87). There were no events meeting criteria for severe hypoglycemia (seizure or loss of consciousness) during the 13 weeks of the study, including no cases in which glucagon or a similar intervention was needed due to lack of responsiveness.
Subjects and parents reported high overall satisfaction with the Navigator on the Continuous Glucose Monitor Satisfaction Scale at 13 weeks with average item scores of 3.6 for subjects and 3.9 for parents on a 5-point Likert scale. Mean item scores were more favorable than “Neutral” (above 3.0) on 42 of the 44 items (95%) for parents and on 40 (91%) of items for children. It is particularly noteworthy that over 70% of both patients and parents agreed that use of the Navigator made adjusting insulin easier (item #2), made them more sure about making diabetes decisions (#3), showed patterns in blood glucose not seen before (#20), clarified how everyday habits affected blood sugar levels (#23) and did not cause more family conflicts (#25) (; available at www.jpeds.com
Continuous Glucose Monitoring Satisfaction Scale at 13 Weeks (N=22* subjects and N=30 parents)
Scores on the Diabetes Self Management Profile (higher score denotes better adherence, possible range 0-86) were similar at baseline and 13 weeks (subjects: 64 ± 11 vs. 63 ± 10, p=0.39; parents: 63 ± 10 vs. 64 ± 10, p=0.69). There were also no meaningful changes in PedsQL scores (lower score denotes higher quality of life, possible range 0-112) over the course of the study (subjects: 26 ± 10 vs. 26 ± 12, p=0.81; parents: 31 ± 9 vs. 31 ± 9, p=0.91).
Most subjects tolerated the Navigator placement well. Two subjects had severe skin reactions related to the adhesive of the sensor mount. When the skin reaction resolved, both subjects resumed Navigator use with an under-bandage placed between the sensor mount and the skin.
At the 13-week visit, 8 (29%) of the 28 subjects had acute skin changes reflective of Navigator use (moderate in 14% and mild in 14%), and 11 (39%) were considered to have non-acute changes such as scabbing 32%, dry skin 21% and changes in pigmentation 7%.