User`s guide

Dexcom G4 User’s Guide | 135
Sensor Stability
Sensors can be worn for up to 7 days. To verify sensors performance over time,
42 sensors were evaluated across the 7-day wear period. Performance was
estimated by calculating the percentage of System readings within 20 mg/dL (1.1
mmol/L) or 20%, 30 mg/dL (1.7 mmol/L) or 30% and greater than 40 mg/dL (2.2
mmol/L) or 40% of the YSI values at the beginning (Day 1), middle (Day 4) and
end (Day 7) of the System lifecycle. The average and median of the absolute
percent differences are included in Table 6 showing consistent accuracy and
sensor stability over the 7-day life of the sensor.
Precision of System Readings
In the same study, all subjects wore two Systems. This was to look at how
similarly two Systems function on the same patient (sensor Precision). Precision
was evaluated by comparing the glucose readings from the two Systems worn
on the same subject at the same time. Results showed that System readings
from the two sensors generally agreed with each other within 8% (absolute
percent difference) and has a 6% coefcient of variation.
Sensor Life
Sensors may be worn for up to 7 days (168 hours). To estimate how long a
sensor will work over 7 days, 42 sensors were evaluated to determine how many
days/hours of readings each sensor provided. Ninety-three percent (93%) of the
sensors lasted until day 7 (145-168 hours). There were 3 (7%) sensors ended
early and lasted until day 4, two of which occurred within the same patient.
Table 6. System Sensor Stability (Accuracy over Time)
Day of
Wear
Number
of Paired
YSI-System
Readings
Mean
Absolute
Percent
Differences
(%)
Median
Absolute
Percent
Differences
(%)
Percent
within 20%
of YSI*
Percent
within 30%
of YSI*
Percent
greater
than 40% of
YSI*
Day 1 506 14% 11% 79% 93% 3%
Day 4 562 16% 14% 75% 93% 2%
Day 7 409 12% 11% 87% 98% 1%
*For YSI less than 80 mg/dL (4.4 mmol/L), the absolute difference is presented as the
difference between the System and YSI, rather than the percent.