Abbott FreeStyle Navigator User Manual page 166

156 Section 18
Appendix B: Specifications
18 Appendix B: Specifications
Performance Relative to the Reference (YSI)
Error grid analysis (like the Clarke Error Grid Analysis and Continuous Glucose-Error Grid Analysis)
is one way to evaluate the accuracy of the FreeStyle Navigator system. The accuracy can also be
assessed by analyzing the difference in the glucose results from the FreeStyle Navigator system when
compared to the results from the YSI. Table 4a shows an analysis of the measure of closeness of the
FreeStyle Navigator system to the YSI. It breaks the data into smaller groups based on the glucose
value reported by the YSI. The table reports the mean absolute difference for the data pairs in each
of the smaller groups. Table 4b shows the same data at different levels of glucose and further groups
them by the amount of difference from the YSI. Table 5 breaks out the overall performance relative to
the YSI for the two sites of sensor insertion.
The overall median absolute relative difference for all the data pairs is 9.3%.
Table 4a. Performance relative to YSI at different glucose levels
Glucose (mg/dL)
20-40
41-80
81-120
121-240
Table 4b. Performance relative to YSI at different levels of glucose – grouped by amount of difference
from the YSI
Glucose Range
(mg/dL)
20-40*
41-80*
81-120
121-240
>241
Overall
*The absolute difference from the YSI reading is measured in mg/dL if the YSI reading is 20-80 mg/dL.
Table 5. Performance relative to YSI at different insertion sites
Overall MeanAbsolute
RelativeDifference
12.8% (Std. Dev. = 13.6%)
Mean Absolute Difference = 32.3 mg/dL
Mean Absolute Difference = 18.1 mg/dL
Mean Absolute Difference = 16.3 mg/dL
Mean Absolute Relative Difference = 11.0%
>240 Mean Absolute Relative Difference = 9.5%
Number of Percent Within
Paired Readings 20% of the YSI
22
1295
3820
11430
3795
20362
Abdomen
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(con't)
Performance
Percent Within
30% of the YSI
31.8 54.5
65.9 82.0
69.5 85.2
85.4 95.1
91.7 98.8
82.3 93.1
MARD by Insertion Site
Arm
13.1% 12.6%
Percent Within
40% of the YSI
72.7
90.7
92.7
98.3
99.9
97.0