USEFULNESS OF REFERENCE MATERIALS IN CALIBRATION OF ENZYME-ACTIVITIES

cr-Amylase, alkaline phosphatase and gamma-glutamyltransferase were st udied in a multicentre evaluation. Analyses were performed on differen t patient samples. Each enzyme was assayed in two different laboratori es at both 30 and 37 degrees C, with widely used reagent kits and with the IFCC reference method (if in existence). Results differed conside rably according to the measurement procedure. Data also showed that it was not possible to employ a constant conversion factor for one enzym e and different techniques between 30 and 37 degrees C. Calibration wi th three reference materials extensively improved the intermethod cons istency for most of the tested measurement procedures. It was possible to transfer accuracy from the method used for the certification of th e reference material to routine procedures, by using the reference mat erial as calibrator. Temperature did not seem to be a crucial variable for the implementation of the enzyme calibrator approach.