Page 329 - Glucose Monitoring Devices

336 CHAPTER 16 The dawn of automated insulin delivery

led to the assessment of the system was done over 4e5 days in a hotel-based study
that included 9 adults and 15 adolescents at three clinical centers. Although time in
target range did not reach statistical significance in the well-controlled adult cohort
(baseline HbA1c 7.0 0.7%), rates of time <70 mg/dL and <60 mg/dL were
reduced fourfold. Meanwhile, the adolescent cohort had higher baseline HbA1c
levels (9.0 1.1%), and in this group, time in the target range of 70e180 mg/dL
increased by nearly 15%.
To obtain market approval, Medtronic designed a 3-month single-arm study of
124 participants to assess the safety of the system. With over 12,000 patient-days
closed-loop control data in a cohort of 14e75-year-olds, there were no episodes
of severe hypoglycemia or diabetic ketoacidosis [99]. Before initiating hybrid
closed-loop insulin delivery, 2-week of baseline data were collected using SAP
therapy [99]. Although the study was not designed with a primary efficacy endpoint,
exploratory analyses demonstrated improvement in glycemic control with a mean
drop in HbA1c of 0.5% [99]. Furthermore, in 94 adults aged 22e75 years old, the
percent of the time in the target range rose from 68.8 11.9 to 73.8 8.4%. Similar
findings were seen in adolescents (n ¼ 30, age 14e21 years) with improvements in
time in target range from 60.4 10.9 to 67.2 8.2% [100]. Data from this study
were submitted to the FDA for premarket approval in June 2016. Just over
100 days later, on September 28, 2016, the device received regulatory approval
for those 14 years and over.
To assess the performance of the system in a pediatric population, a similar study
design was employed in 105 youth with T1D aged 7e13 years. The median use of
auto mode use was 81% of the time, and there were no episodes of severe hypogly-
cemia or diabetic ketoacidosis during the study period. HbA1c fell on average 0.4%
from baseline with a concomitant 9% rise in time in target range over the 24 h
period. By June 2018, the FDA lowered the age for which the device was approved
to 7 years, and the Conformite ´ Europe ´nne (CE) Mark for the device mirrored this.
Most recently, data have been reported on the use of the system in very young
children, between the ages of 2e6 years [101]. As had been demonstrated in the
studies of both older children and adults, in this study of 42 participants, there
were no episodes of severe hypoglycemia or DKA. Furthermore, time in range
increased 8% primarily mediated through a reduction in time spent in the hypergly-
cemic range leading to an average reduction in A1c by 0.5% [101].

Exploring the equipment: components and characteristics of
the 670G
Guardian sensor 3
The Medtronic 670G automates insulin delivery based on sensor glucose readings
obtained with the Guardian Sensor 3. The sensor requires fingerstick calibrations
at least every 12 h to display sensor data. Although it has been cleared for automated