8-12 Operator’s Manual – OPTI CCA-TS
8.5.9 Limitations
The OPTI CCA-TS system is designed to measure whole blood, serum, or plasma, to be controlled with
Standard Reference Cassettes on a daily basis, and with aqueous solutions for each new lot of cassettes.
Aqueous controls are portable and quite convenient to use with the OPTI CCA-TS system, however, their
low oxygen carrying capacity and temperature sensitivity is well known. Measurements of such materials
are more prone to pre-analytic error as well as analyzer-specic errors, compared to similar measurements
of whole blood. The OPTI CCA-TS system is no exception to this, and demonstrates somewhat poorer
PO
2
precision with aqueous controls than with whole blood, due to the large amount of plastic material
comprising its disposable measurement chamber.
The OPTI CCA-TS’s tHb measurement is sensitive to pathologically rapid sedimentation rates of the
erythrocytes, often induced by excessive rate and amounts of rouleaux formation
4
. This is observable as
rapid sedimentation and clarication due to erythrocyte aggregates falling to the bottom of the syringe
within minutes of mixing. The OPTI CCA-TS breaks up most of the rouleaux and other aggregates by
rapidly aspirating the whole blood sample with high shear rate, however in rare pathologic cases the
rouleaux aggregates persist or reform during the aspiration and cause a positive tHb offset of up to 3 g/dL,
typically within the range 7-12 g/dL.
Any measurement outside the Measurement Range will be indicated on the display as ‘ LOW ‘ for values
lower than the range and ‘ HIGH ‘ for values above the range. However, the printed report will show out-
of-range values with reference to the end value of the measurement range; for example, the printed report
will show a PCO
2
value of 220 mmHg as:
PCO
2
> 200 mmHg (Meas.Lim)
For measurement ranges of the individual analytes, see Analyte Section of this Operator’s Manual.
3
Mahoney JJ, Wong RJ, Van Kessel AL, Reduced Bovine Hemoglobin Solution Evaluated for Use as a
Blood Gas Quality Control Material. Clin.Chem.39/5,874-79 (1993)
4
J.B.Henry, Clinical Diagnosis and Management by Laboratory Methods, 19th Ed., 1996, p.590,777
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