18 appendix b: specifications, Con’t) – Abbott Freestyle PRT03831-xxx User Manual
Page 166
18 Appendix B: Specifications
(con’t)
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)
Performance
20-40
Mean Absolute Difference = 32.3 mg/dL
41-80
Mean Absolute Difference = 18.1 mg/dL
81-120
Mean Absolute Difference = 16.3 mg/dL
121-240
Mean Absolute Relative Difference = 11.0%
>240
Mean Absolute Relative Difference = 9.5%
Table 4b. Performance relative to YSI at different levels of glucose – grouped by amount of difference
from the YSI
Glucose Range
(mg/dL)
Number of
Paired Readings
Percent Within
20% of the YSI
Percent Within
30% of the YSI
Percent Within
40% of the YSI
20-40*
22
31.8
54.5
72.7
41-80*
1295
65.9
82.0
90.7
81-120
3820
69.5
85.2
92.7
121-240
11430
85.4
95.1
98.3
>241
3795
91.7
98.8
99.9
Overall
20362
82.3
93.1
97.0
*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
MARD by Insertion Site
Abdomen
Arm
12.8% (Std. Dev. = 13.6%)
13.1%
12.6%
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156
Section 18
Appendix B: Specifications