[Analytical performances of the i-STAT portable clinical analyzer for the measurement of PO2 and PCO2].

Aware of some limitations on blood gas results, we performed an extensive evaluation before introducing i-STATs in our hospitals. Three i-STATs were tested in parallel with an ABL-520, on three types of cartridges (EG7, EG6 and EG3), using tonometered whole blood (9 gas levels, n = 720) and aqueous QC solutions (3 levels, n = 600). Reference systems were the theoretical calculated values from gas composition used for tonometry and results given by the ABL-520, respectively.

Evaluation of syringes for ionized calcium measurements.

Unlabelled: Commercially available ready to use syringes (Radiometer, Sarstedt, Ciba-Corning and Portex), containing heparinate as an anticoagulant have been tested to evaluate the magnitude of induced preanalytical errors. Tonometered serum pools adjusted to four Ca2+ concentrations were sampled anaerobically.

Measurements: Ca2+ and pH (ICA2 with 3 digits, Radiometer Medical A/S, Denmark; Heparin: anti-Xa factor activity on a chromogenic substrate.

Evaluation of capillaries for ionized calcium measurements.

Commercially available capillaries containing calcium-titrated heparinate as an anticoagulant designed specifically for ionized calcium measurements in blood were tested with four serum pools with ionized calcium concentrations adjusted to 0.75, 1.25, 1.

Use of calcium-titrated sodium heparinate for ionized calcium determination on plasma and whole blood (heparinized blood sampler B-129 Radiometer).

We report modifications of ionized calcium as observed on specimens collected in a commercially available sampling device (Radiometer B-129). When the sampler is used as recommended, errors are non-significant around 1.25 mmol l-1.

In vitro evaluation of a heparinized blood sampler for ionized calcium measurement.

When ionized calcium measurements are needed urgently blood has to be sampled with an anticoagulant to allow rapid specimen processing. Heparinate salts cause a decrease in ionized calcium by binding which is clinically significant when the concentration exceeds 15 IU/mL of whole blood. The use of an anticoagulant in an aqueous state induces 'solution-dilution' errors.

Preanalytical errors in ionized calcium measurements induced by the use of liquid heparin.

The use of heparin in a liquid form to measure ionized calcium (Ca++) in plasma or whole blood can induce preanalytical errors by dilution and by changing the original Ca++ value by binding or by re-equilibration with calcium in the anticoagulant solution. To quantify these errors, Ca++ was measured on serum pools under different sampling conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested.

Anomalies in pH 7.40 correction in ionised calcium analysers.

As a preliminary step in a study of the effects of calcium ligands on the pH standardisation of ionised calcium (Ca2+) measurement in blood, the change in Ca2+ induced by Pco2 variation was investigated in 12 serum pools on three different instruments. This type of study should yield a log Ca2+ = f(pH) linear relationship in a pH range around pH 7.40 with a slope characterising the pH-sensitive calcium buffer capacity of the specimen.

Anticoagulant-induced preanalytical errors in ionized calcium determination on blood.

When anticoagulated blood is necessary for ionized calcium (Ca2+) measurements especially in urgent circumstances, the type (sodium or 'calcium-titrated' heparinate) as well as the form (aqueous or dry) of anticoagulant induce preanalytical errors. To quantify these modifications Ca2+ was measured in three aqueous solutions and in three serum pools in different 'sampling' conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested.

Inadequate algorithm: a cause for 'incorrect pH 7.40 correction' in ionized calcium analysers.

As a preliminary step in a study of the effects of calcium ligands on the pH standardization of ionized calcium (Ca2+) measurements in blood, the slope of logCa2+ = f(pH) linear relationship characterizing the pH-sensitive calcium buffer capacity of the specimen was investigated in 12 serum pools on three different instruments. The pH 7.40 correction line should be horizontal.