Use of Novel Preparations of Heparin to Eliminate Interference in Ionized Calcium Measurements: Have All the Problems Been Solved?

A long-standing concern in rapid measurement of ion-ized calcium is the interference from heparin used as an anticoagulant. Although serum may be obtained and analyzed without use of anticoagulant, clotting and con-trifugation add to the turnaround time and can present variable artifacts (1, 2). Very little heparin (-1 IU/mL) is required to inhibit coagulation. One molecule of hep-arm catalyzes the binding between many molecules of antithrombin III and thrombin, thereby preventing the conversion of fibrinogen to fibrin. “Liquid heparin ” (i.e., heparin in solution) readily mixes with blood, but use of liquid heparin in blood-collection devices is declining for a variety of reasons. Now that instruments have been developed for analyz-ing blood gases, electrolytes, glucose, lactate, magne