Abbott i-STAT 1 System Manual page 454

The reference ranges programmed into the analyzer and shown above are intended to be used as guides
for the interpretation of results. Since reference ranges may vary with demographic factors such as age,
gender, and heritage, it is recommended that reference ranges be determined for the population being
tested.
Clinical Significance
TCO is a measure of carbon dioxide which exists in several states: CO
2
bound to proteins, bicarbonate (HCO
of TCO as part of an electrolyte profile is useful chiefly to evaluate HCO
2
useful in the assessment of acid-base imbalance (along with pH and PCO
Calculated and Measured (Traceable) TCO
The calculated TCO provided by the i-STAT System is determined from the measured and reported values
2
of pH and PCO according to a simplified and standardized form of the Henderson-Hasselbalch equation.
2
measurement is metrologically traceable to the i-STAT pH and PCO
This calculated TCO
2
which are in turn traceable to primary standard reference materials for pH and PCO
parameters reported by the i-STAT System, the user can independently determine TCO
reported pH and PCO
2
Cartridge and Test Information (CTI) sheet, and the equation for TCO
On the CHEM8+ cartridge, TCO
implication of direct traceability to this TCO
reference materials – is subtle but significant: the CHEM8+ is independent of the pH and PCO
Given the metrological traceability of the CHEM8+ TCO
be a measured analyte.
Performance Characteristics
Precision data were collected in multiple sites following the protocol recommended by Abbott Point of
Care. The means, SDs and CVs from 20 replicates at each site were averaged. The average statistics are
presented below.
Method comparison data were collected using CLSI guideline EP9-A.
collected in lithium heparin evacuated tubes from hospital patients. The whole blood samples were run
in duplicate on the i-STAT System. The samples were then centrifuged to obtain plasma and analyzed in
duplicate on the comparative instrument. All samples were analyzed on both methods within 15 minutes
of each other.
Deming regression analysis
table, n is the number of specimens in the first data set. Sxx and Syy refer to the 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 may vary from site to site due to differences in sample handling, comparative method
calibration and other site specific variables. For TCO
analyzers may be slightly lower than TCO
anaerobic handling. Up to 6 mmol/L CO
6
*The usual warning relating to the use of regression analysis is summarized here as a reminder. For any analyte, "if the data is a narrow range, the
estimate of the regression parameters are relatively imprecise and may be biased. Therefore, predictions made from estimates may be invalid",
correlation coefficient, r, can be used as a guide to assess the adequacy of the comparative method ranges in overcoming the problem. As a guide, the
range of data can be considered adequate if r>0.975.
TCO2 - 2
) or carbonate (CO
3
2
TCO = HCO
2
measurements using a combination of the equation for HCO
is metrologically traceable to the IFCC TCO
2
reference method – and not to pH and PCO
2
was performed on the first replicate of each sample. In the method comparison
5
calculated from pH and PCO
2
can be lost per hour by exposure of the sample to air.
2
Art: 716661-01G
in physical solution or loosely
2
) anions, and carbonic acid (H
3
concentration. TCO
3
) and electrolyte imbalance.
2
+ 0.03 PCO
3 2
above.
2
measurement, the traceable TCO
2
Venous blood samples were
4
, values measured on serum or plasma by chemistry
2
due to loss of CO
2
CO ). Measurement
2 3
and HCO are
2 3
3
measurements,
2
. Like all calculated
2
values from the
2
given in the PCO
3
reference method. The
2
standard
2
traceability.
2
is considered to
2
during non-
2
7
The
4
Rev. Date: 01-Jul-13
2