Introduction. It was shown by a number of studies that characteristics of materials used for quality control (QC) are not identical to the natural samples characteristics. Nevertheless, QC materials remain irreplaceable for daily variance assessment, but the information provided by QC measurements could be insufficient if different equipment for the analysis of the same analyte is in use at the same laboratory.
Aim of the study. The aim of the study was to adopt split-sample testing for expanded QC - comparison of test results measured with separate instruments on the same natural sami ples.
Results. It was shown that results of all tested analytes except alkaline phosphatase (ALP) were near to ideal: slope of agreement by Passing-Bablock a supplement of traditional QC to make trends of divergent results more evident.
Conclusions. It was shown QC and EQA results to be not sufficient for demonstrating divergent results of two identical analytical systems covering the linearity range. Split-sample testing allowed us to demonstrate the difference of ALP results performed on identical analytical systems.
