EVALUATION OF SYRINGES FOR IONIZED CALCIUM MEASUREMENTS

Commercially available ready to use syringes (Radiometer, Sarstedt, Ci ba-Corning and Porter), 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 sa mpled anaerobically. Measurements: Ca2+ and pH (ICA2 with 3 digits, Ra diometer Medical A/S, Denmark; Heparin: anti-Xa factor activity on a c hromogenic substrate. Results were expressed as means of 10 measuremen ts and as percentages of the reference values. Sarstedt syringes, (Li- heparinate), yielded a negative bias (-3%). However for 0.5 or 1 mL sa mples 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%. Porter (Pulsator) syringes showed biases above +4% even for nominal sampling volumes. A ll syringes (except Pulsator) released anticoagulant amounts correspon ding to the expected values. Radiometer and Ciba-Coming were the only recommendable devices.