Abbott Freestyle PRT03831-xxx - Manual (Page 165)

OVER
18 Appendix B: Specifications
(con’t)
Table 2 is a summary of the statistics that describe how well data from the FreeStyle Navigator system
correlates to the results from the reference method. Glucose results from the FreeStyle Navigator
system and the corresponding results from the YSI (a total 20362 pairs of data points) in the In-
Clinic study were used to determine the correlation.
YSI Reference (mg/dL)
N
av
ig
at
or CM (m
g/dL)
Figure 1.
y = x
Table 3a displays the distribution of all the data from the In-Clinic study on the Clarke Error Grid.
It breaks the data set into smaller groups based on the glucose value reported by the YSI. For each of
these smaller groups, the table shows what percentage of data fall into different zones of the grid.
Table 3a.
Accuracy performance at different glucose levels using the Clarke Error Grid Analysis
Reference
Glucose Level
(mg/dL)
Number of
Paired
Readings
A and B
(%)
A
(%)
B
(%)
C
(%)
D
(%)
E
(%)
20-40 22 54.5 54.5 N/A* N/A* 45.5 0.0
41-80 1295 77.7 55.2 22.5 0.0 22.3 0.0
81-120 3820 99.9 69.5 30.4 0.1 N/A* N/A*
121-240 11430 99.9 85.4 14.4 0.1 N/A* 0.0
241+ 3795 99.5 91.7 7.8 0.0 0.4 0.1
Overall 20362 98.3 81.7 16.7 0.1 1.6 0.0
*N/A means that the Clarke Error Grid does not consider the possibility of these zones in that
concentration range.
Table 3b displays the same data as in table 3a on the Continuous Glucose-Error Grid. This is
a modified error grid that is designed to evaluate the clinical accuracy of continuous glucose
monitoring systems based on both glucose data points in time and the rate of change of glucose.
Table 3b.
Accuracy performance at different glucose levels using the Continuous Glucose-Error Grid
Analysis
Zone
YSI ≤ 70 mg/dL
70 mg/dL < YSI
≤180 mg/dL
YSI > 180 mg/dL All
N % N % N % N %
Accurate
Readings
369 59.5 10407 98.9 8364 98.6 19140 97.5
Benign
Errors
5 0.8 99 0.9 74 0.9 178 0.9
Erroneous
Readings
246 39.7 22 0.2 41 0.5 309 1.6
ALL 620 100.0 10528 100.0 8479 100.0 19627 100.0
Slope 0.92
Intercept 14.3 mg/dL
Correlation Coefficient (r) 0.93
N
20362
Range 25 – 533 mg/dL
Overall mean bias +0.8 mg/dL
Table 2. Regression Analysis. FreeStyle
Navigator System (mg/dL) vs the YSI (mg/dL)
Section 18 155
Appendix B: Specifications
B
B
A
A
C
E
D D
E
C
0 100 200 300 400 500
500
400
300
200
100
0