Two studies on the trueness of enzyme measurement were shortly compared and explained. First, highly organized EC4 study obtained practically the same results as routinely performed EQA program despite total different approach to problem. EC4 study worked with six fully homogenous measurement systems from leading world manufacturers, while participants of EQA used very heterogenic systems which consisted of equipment, reagents and calibrators from different producers. The best trueness showed in both studies measurement of ALT and AST, significant bias was determined in gamma-GT and CK measurement. Bias and traceability of α-amylase and LD seems to be better in Czech labs than in participants of EC4 study. Use of target values as criterion in EQA and strictly requirement to use only measurement methods based on the same principles as reference IFCC procedures can be way to trueness and traceability of enzyme measurement results.

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