Theoretical and Experimental Evidence in Mixed Serum Samples as Natural Reference Materials for Measuring Activity of Biomacromolecules in Serum.

Background: The target substances of biomacromolecules are primarily unstable in biological, chemical, and immunological activity, whereby, the standardized substances are obtained with considerable difficulty. We explored the possibility of using a mixed serum sample as a natural reference material for measurement of biomacromolecules in serum. Methods: Eight serum samples were selected randomly from a clinical laboratory. Then, 2, 4, and 8 serum samples were mixed (in equal quantity) resulting in 4, 2, and 1 sample groups, respectively, to compare mean measurement results of biochemical indices between single samples and mixed samples. Moreover, 40 serum samples were selected randomly from a clinical laboratory. From those samples, three groups were set up comprising 20, 10, and 5 sample groups by mixing equal quantities of 2, 4, and 8 serum samples, respectively. These samples were used to compare standard deviation (SD). The sixteen indices tested comprised proteins, enzymes, and organic molecules and were measured by an automatic biochemical analyzer. Results: The mean values from mixed samples were much closer to the mean values from the single serum samples. The SD values of the 2, 4, or 8 mixed serum samples were close to the expected value. Conclusions: These data suggest that the design of the reference material (i.e., a mixed serum sample) was suitable for the measurement of biological samples.