Abbott i-STAT 1, Системное руководство

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Rev. Date: 02-Aug-11 Art: 714182-00R
PCO2 - 3
Temperature “Correction” Algorithm
PC
O
2
is a temperature-dependent quantity and is measured at 37°C. The
PC
O
2
reading at a body
temperature other than 37°C can be ‘corrected’ by entering the patient’s temperature on the chart page of
the analyzer. See section 12 ‘Procedure for Cartridge Testing’ in the i-STAT 1 System Manual or section 11
‘Patient and Control Sample Testing’ in the i-STAT System Manual for details. In this case, blood gas results
will be displayed at both 37°C and the patient’s temperature. The
PC
O
2
at the patient’s temperature (T
p
) is
calculated as follows
1
:
Note: Patient temperature corrected results are available only on cartridges containing pH, P
CO
2
, and
P O
2
sensors.
Performance Characteristics
The performance characteristics of the sensors are equivalent in all cartridge configurations.
The typical performance data summarized below was collected in a health care facility by health care
professionals trained in the use of the i-STAT System and comparative methods.
Precision data were collected in multiple sites as follows: Duplicates of each control fluid were tested in the
morning and in the afternoon on five days for a total of 20 replicates. The averaged statistics are presented
below.
Method comparison data were collected using CLSI guideline EP9-A
5
.
Venous blood samples were
collected in blood gas syringes. All samples were analyzed in duplicate on the i-STAT System and on
the comparative methods within 10 minutes of each other. Arterial blood samples were collected from
hospital patients in 3cc 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
6
was performed on the first replicate of each sample. In the method comparison
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”.
7 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
Mean SD %CV
Level 1 63.8 1.57 2.5
Level 3 19.6 0.40 2.0