Abbott i-STAT 1 System Manual page 441

Method comparison data were collected using CLSI guideline EP9-A.
collected from hospital patients in 3 cc blood gas syringes and were analyzed in duplicate on the i-STAT
System and the comparative method within 5 minutes of each other.
Deming regression analysis
table, n is the number of specimens in the data set, Sxx and Syy refer to estimates of imprecision based
on the duplicates of the comparative and the i-STAT methods respectively, Sy.x is the standard error of
the estimate, and r is the correlation coefficient.* Method comparisons will vary from site to site due to
differences in sample handling, comparative method calibration and other site specific variables.
* The usual warning relating to the use of regression analysis is summarized here as a reminder: For any analyte, "if the data is collected over a narrow
range, the estimate of the regression parameters are relatively imprecise and may be biased. Therefore, predictions made from these estimates may be
invalid". 6 The correlation coefficient, r, can be used as a guide to assess the adequacy of the comparative method range in overcoming this problem.
As a guide, the range of data can be considered adequate if r>0.975.
Precision Data (mmHg)
Aqueous Control
Level 1
Level 3
Method Comparison (mmHg)
Radiometer
ABL500
n 45
Sxx 3.70
Syy 2.78
Slope 1.023
Int't -2.6
Sy.x 2.52
Xmin ----
Xmax ----
r 0.996
Factors Affecting Results*
Exposure of the sample to air will cause an increase in PO
decrease in PO when values are above 150 mmHg (approximate PO
2
Standing anaerobically at room temperature will decrease pH at a rate of 0.03 per hour, will increase PCO
by approximately 4 mmHg per hour and will decrease PO
Do not ice samples before testing – PO
cartridge – PO results may be falsely decreased if the cartridge is cold.
2
*It is possible that other interfering substances may be encountered. These results are representative and your results may differ somewhat due to
test-to-test variation. The degree of interference at concentrations other than those listed might not be predictable.
Factors Affecting Calculated Results
values calculated from a measured PO
sO
2
significantly from the direct measurement.
Rev. Date: 01-Jul-13
was performed on the first replicate of each sample. In the method comparison
5
Mean SD
65.1 3.12
146.5 6.00
Radiometer
ABL700
29
2.04
2.64
0.962
1.2
3.53
39
163
0.990
results may be falsely elevated in cold samples. Do not use a cold
2
and an assumed oxyhemoglobin dissociation curve may differ
2
3
Art: 714180-01L
Arterial blood samples were
4
%CV
4.79
4.10
Bayer 845
30
3.03
3.28
1.033
-2.9
3.44
31
185
0.996
when values are below 150 mmHg and a
2
of room air).
2
at a rate of 2–6 mmHg per hour.
2
2
6
PO2 - 3