MULTICENTER HARMONIZATION OF COMMON ENZYME RESULTS BY FRESH PATIENT-POOL SERA

A region consisting of 19 clinical laboratories harmonized their calib ration of seven common enzymes by using fresh patient-pool sera. One o f the laboratories was chosen to act as Regional Reference Laboratory (RRL). This laboratory used internationally accepted (mostly IFCC) met hods at 37 degrees C, with an intralaboratory CV less than or equal to 2.5%. First, the reference ranges of the RRL were verified by analysi s of a reference population and calculation of the results by a parame tric method. Next, all laboratories, including the RRL, received six p atient-pool sera and analyzed them at the same time on the same date. Enzyme calibration factors at each laboratory were converted on the ba sis of the slope, and occasionally the intercept, of regression analys is with the RRL and the individual laboratory. Before harmonization, t he interlaboratory CVs varied from 16.9% to 61.6%. After harmonization , CVs decreased to between 5.0% and 9.5%. These results proved to be r eproducible over a period of more than a year. Using internationally a ccepted inaccuracy and imprecision criteria, the achieved interlaborat ory CVs permit the use of one set of reference ranges by all participa ting laboratories. Certified Reference Materials were analyzed, result ing in interlaboratory CVs as low as those achieved with patient-pool sera. These materials can act as commutable reference preparations, ex cept for creatine kinase.