Dexcom G4 Platinum User Manual page 165

Accuracy Relative to YSI
Accuracy between matched pairs was also estimated by calculating the
percent difference between the System reading and the YSI value. For
example, if the YSI value is 100 mg/dL (5.6 mmol/L) and the System
reading is 90 mg/dL (5.0 mmol/L), a 10% difference between the System
and the YSI is reported. The System and YSI values were compared
by pairing the System reading that occurred immediately after the YSI
sample was collected.
In the example above, the System reading is less than the YSI value, so
the percent difference reading is negative. The mean percent difference
is the average of all positive and negative percent differences between
the two devices; it tells you if the System reads higher or lower on
average than the YSI within each glucose range.
Another estimate used to show the accuracy of the System is the
absolute percent difference. The absolute percent difference tells
you the percent difference or "distance" between the System and YSI
values, but does not tell you whether the System 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 System readings and YSI values.
These accuracy measures in differences are based on 2922 paired
glucose results and summarized in the following tables. Tables 4-A and
Table 4-B represent the system difference within CGM glucose ranges
from the pediatric and adults studies, respectively.
Dexcom G4 PLATINUM (Pediatric) System User's Guide | 163