MULTIENZYME CONTROL SERUM (SERACLEAR-HE) CONTAINING HUMAN ENZYMES FROM ESTABLISHED CELL-LINES AND OTHER SOURCES .3. EVALUATION AS CANDIDATEWORKING ENZYME REFERENCE MATERIAL FOR GAMMA-GLUTAMYL-TRANSFERASE

Seraclear-HE, containing gamma-glutamyltransferase (GGT, EC 2.3.2.2) d erived from the cell culture of a human macrophage cell line, was eval uated as a candidate enzyme reference material (ERM) to calibrate rout ine methods in terms of a Reference Method for GGT, We have compared t his preparation with commercially available materials, including Certi fied Reference Material 319, at 30 degrees C and 37 degrees C with res pect to kinetic properties and with respect to commutability between t he Reference Method and each of 15 analytical procedures involving fir e structurally different donor substrates, GGTs of human origin are fa r more commutable with reagents of varied types than are GGTs derived from animals, Calibration of 44 patients' sera with Seraclear-HE decre ased average intermethod variation from 20% to similar to 4%, whereas GGTs of animal origin showed intermethod variations of similar to 30% with no benefit from calibration, Seraclear-HE is promising as a secon dary or working ERM to be used as an intermethod calibrator.