SEVEN PLUS User’s Guide | 113
In the above example the SEVEN PLUS 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 SEVEN PLUS on average reads higher or lower than the YSI at each
glucose range. Another estimate used to tell you the accuracy of the SEVEN PLUS is the
absolute percent difference. The absolute percent difference tells you the overall percent
difference or “distance” between the SEVEN PLUS and YSI readings, but does not tell you if
the SEVEN PLUS 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 SEVEN PLUS readings and YSI readings. These accuracy measures are summarized
in Table 4 below and are based on 1,827 paired glucose measurements:
Table 4. SEVEN PLUS 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%
Table 4 shows that the SEVEN PLUS, on average, reads 13% higher than the YSI at glucose levels of 40-80 mg/
dL and reads 9% lower, on average, than the YSI at glucose concentrations of 301-400 mg/dL (Mean Percent Differ-
ence). The SEVEN PLUS reads, on average, 25% different than the YSI at glucose levels of 40-80 mg/dL and, on
average, 13% different than the YSI readings at glucose levels of 301-400 mg/dL (Mean Absolute Percent Difference).
The Median Percent Difference shows that 50% of the time the SEVEN PLUS reads approximately 3% less than the
YSI System and the Median Absolute Difference shows that 50% of the time the SEVEN PLUS reads about 13%
different then YSI blood glucose readings taken within 5 minutes.
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