Evaluation of syringes for ionized calcium measurements

Abstract

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. Results were expressed as means of 10 measurements and as percentages of the reference values.

Sarstedt syringes, (Li-heparinate), yielded a negative bias (-3%). However for 0.5 or 1 mL samples the bias reached -4% to -6%.

Radiometer syringes (QS50 and QS90; calcium titrated heparinate) demonstrated biases below -2%.

The bias in the Ciba-Corning (Gas-Lyte) syringe was below 2%.

Portex (Pulsator) syringes showed biases above +4% even for nominal sampling volumes.

All syringes (except Pulsator) released anticoagulant amounts corresponding to the expected values.

Radiometer and Ciba-Corning were the only recommendable devices.

Key Words:

• Heparinate
• preanalytical error
• sampling volume