OPTi CCA-TS2 - Page 189

pH-2 Operator’s Manual – OPTI CCA-TS2
pH ANALYTES
Interferences
Optode pH measurements have a known sensitivity to the blood ionic strength
3
, which is determined
primarily by variation in serum levels of sodium. The OPTI CCA-TS2 utilizes an internal Na
+
sensor
to actively compensate and correct for this sensitivity. That is, the OPTI CCA’s reported pH has no
measurable interference from hyponatremic or hypernatremic samples, nor for ionic strength variations
within the physiologic limits of 100 to 190 mmol/L.
Heparin salts are the only acceptable anticoagulants. Other anticoagulants such as citrate, EDTA, oxalate,
and uoride cause signicant interferences to the pH sensor.
The following exogenous interferents were quantied in tonometered plasma, showing interferences to
dyes which typically have short half-lives within the body before being metabolized by the liver.
This testing was done on the OPTI CCA platform, with a standard OPTI style pH sensor. No changes
were made to the sensor or the measurement principle, so the interference of the OPTI CCA-TS2 is
equivalent to the OPTI CCA.
Substance Amount pH change
Sodium uorescein 26 mg/dL unstable
Cardio (indocyanine) green 0.5 mg/dL -0.04
Methylene blue 25 mg/dL -0.16
Only clear, uncolored quality control materials, such as OPTI CHECK or OPTI CHECK PLUS brand
aqueous controls should be used with the OPTI CCA-TS2 system. Colored materials, including
prociency testing materials, may interfere with the pH measurement, or fail to be properly aspirated.
Reproducibility
Controls
Within run precision (S
wr
) and Total Precision (S
T
), were determined from 2 runs per day with 2 replicates
per run over a period of 20 days following the CLSI guideline EP5-A2. Typical results for 3 different
control levels are shown below.
pH OPTI Check Level 1 OPTI Check Level 2 OPTI Check Level 3
Days Run 20 20 20
Total Average 7.151 7.415 7.624
Within Run St. Dev. (S
wr
) 0.003 0.006 0.005
Within Run % CV 0.0% 0.1% 0.1%
Total Precision St. Dev. (S
T
) 0.005 0.007 0.007
Total % CV 0.1% 0.1% 0.1%