Dexcom SEVEN User Manual page 117

Performance of High and Low Glucose Alerts at night comparing the Seven System to
YSI data has not been established with the Seven Sensor. During use of the device at
home, the High Alert was set at 200 mg/dL and the Low Alert was set at 80 mg/dL. The
Seven System data was compared to the OneTouch Ultra data collected during home
use. Analysis of the home use data showed that when the Seven System was above 200
mg/dL, 18% of the OneTouch Ultra meter readings were actually below 200 mg/dL (False
High Alert). When the Seven read below 80 mg/dL, the OneTouch Ultra was actually
reading above 80 mg/dL 34% of the time (False Low Alerts).
ACCURACY
Accuracy between matched pairs was also estimated by calculating the percent
difference between the Seven System reading and the YSI reading. The Seven System and
YSI readings were compared by pairing the Seven System reading that fell within 2.5 to 7.5
minutes after the YSI reading was collected. For example, if the YSI reading is 100 mg/dL
and the Seven System reading is 90 mg/dL, there is a 10% difference between the Seven
System and the YSI Laboratory machine.
In the above example the Seven System reading is less than YSI reading and so the
percent difference reading is negative. Another estimate used to tell you the accuracy
of the Seven System is the absolute percent difference. The absolute percent difference
tells you the overall percent difference or "distance" between the Seven System and YSI
readings, but does not tell you if the Seven System is reading higher or lower than the YSI
laboratory standard. The mean percent difference is the average of all of the positive and
negative percent differences between the two devices compared and therefore tells you
if the Seven System on average reads higher or lower than the YSI at each glucose range.
The mean absolute percent difference is the average "distance" (regardless if positive or
negative) between Seven System readings and YSI readings.
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