User's Manual

134 | Continuous Glucose Monitoring System
11
Accuracy
Accuracy between matched pairs was also estimated by calculating the percent
difference between the G4-Global Receiver reading and the YSI reading. The
G4-Global Receiver and YSI readings were compared by pairing the G4-Global
Receiver reading that fell approximately 5 minutes after the YSI reading was
collected. For example, if the YSI reading is 100 mg/dL and the G4-Global
Receiver reading is 90 mg/dL, a 10% difference between the G4-Global
Receiver and the YSI Laboratory machine is reported.
In the above example the G4-Global Receiver reading is less than the YSI
reading and so the percent difference reading is negative. 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 G4-Global
Receiver on average reads higher or lower than the YSI at each glucose range.
Another estimate used to tell you the accuracy of the G4-Global Receiver is
the absolute percent difference. The absolute percent difference tells you the
overall percent difference or “distance” between the G4-Global Receiver and
YSI readings, but does not tell you if the G4-Global Receiver is reading on
average higher or lower than the YSI laboratory standard. The mean absolute
percent difference is the average “distance” (regardless if positive or negative)
between G4-Global Receiver readings and YSI readings. These accuracy
measures are summarized in Table 4 below and are based on 1,827 paired
glucose measurements:
Table 4. G4-Global Receiver and YSI Blood Glucose Accuracy by Glucose
Concentration
Glucose
Range
(mg/dL)
Number
of Paired
Readings
Mean
Percent
Difference
Median
Percent
Difference
Mean
Absolute
Percent
Difference
Median
Absolute
Percent
Difference
Overall
(40-400
mg/dL)
1827 -1% -3% 16% 13%
40-80 277 13% 12% 25% 20%
81-180 801 -1% -2% 15% 13%
181-300 563 -6% -7% 13% 12%
301-400 186 -9% -9% 13% 10%
Section 11.1
Placeholder for G4-Global Receiver Pivotal Study Results