Multienzyme control serum (Seraclear-HE) containing human enzymes from established cell lines and other sources. 3: Evaluation as candidate working enzyme reference material for gamma-glutamyltransferase.

Seraclear-HE, containing gamma-glutamyltransferase (GGT, EC 2.3.2.2) derived from the cell culture of a human macrophage cell line, was evaluated as a candidate enzyme reference material (ERM) to calibrate routine methods in terms of a Reference Method for GGT. We have compared this preparation with commercially available materials, including Certified Reference Material 319, at 30 degrees C and 37 degrees C with respect to kinetic properties and with respect to commutability between the Reference Method and each of 15 analytical procedures involving five structurally different donor substrates. GGTs of human origin are far more commutable with reagents of varied types than are GGTs derived from animals. Calibration of 44 patients' sera with Seraclear-HE decreased average intermethod variation from 20% to approximately 4%, whereas GGTs of animal origin showed intermethod variations of approximately 30% with no benefit from calibration. Seraclear-HE is promising as a secondary or working ERM to be used as an intermethod calibrator.