Dexcom G5 User Manual page 316

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.
Accuracy measures in differences for both the Original Adult and Software 505 Adult Studies are
Original Pediatric
summarized in Table 4-A. Accuracy measures in differences for both the and
Software 505 Pediatric
Studies are summarized in Table 4-B. Table 4-A and 4-B are categorized
within CGM glucose ranges.
Software 505 Adult
For example, in the Study (Table 4-A), overall, on average, the system reads
2.5% different (Mean Percent Difference) than the reference and 9.0% absolute different (Mean
Absolute Difference) than the reference values. The Median Percent Difference shows that half of
the time the system reads 2.4% or less than the YSI BG values and the Median Absolute Percent
Difference shows that half of the time the system reads about 7.0% or less than the YSI BG values.
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