Abstract
The present work aims at accessing the stability of biological material stored for diagnostic and scientific purposes. The influence of the temperature, storage time, and cyclic thawing on concentration stability of selected oxidative stress parameters in human serum was investigated. The study group consisted of 20 serum samples collected from healthy volunteers aged 18–52. The parameters whose reference ranges were not determined and to which validated determination methods did not correspond were examined by manual methods (FRAP and AOPP). Automatic methods were used to determine routine laboratory tests (albumin, total protein, bilirubin, uric acid) using the Konelab 20i® analyzer. The samples were stored at various temperatures (room temperature, 4 °C, −20 °C, −80 °C) for max 6 months and were subjected to cyclic thawing at 1 month intervals. In order to check whether any differences between the concentrations of the studied parameters existed when the samples were stored in various conditions, the paired Student t-test or Wilcoxon test and comparison to desirable bias were applied. Based on the obtained results, it was found that the temperature and time of serum sample storage significantly affected the stability of the analyzed parameters and determined different shelf lives of serum samples for oxidative stress examination. Therefore, continuing the investigation concerning the impact of storage conditions on various serum parameters seems justified due to the discrepancy between the individual results obtained by different researchers and the inconsistencies between the results of scientific research and the applicable recommendations.
Highlights
Results of clinical laboratory tests constitute an integral part of clinical medicine and are necessary to make decision about patients’ treatment [1]
Apart from AOPP and FRAP, which are considered to be markers of oxidative–antioxidant balance, some other parameters that we studied may participate in oxidative stress
This is due to the fact that the material collected in this study from individual patients behaves in a different way, which was verified by us, and the results of this examination are presented as: plots of the coefficient of variation for determinations carried out in samples stored in various conditions (Figures S1–S6); correlation coefficient of variation (CV) calculated for specific storage condition with initial concentration (T0 ) (Table S1); changes in concentration of analysed parameters after storage in dependency on time and temperature (Figures S7–S12); available in supplementary materials
Summary
Results of clinical laboratory tests constitute an integral part of clinical medicine and are necessary to make decision about patients’ treatment [1]. The growing number of available laboratory tests, research projects, and biobanking procedures gives the opportunity to explore the previously unknown areas of medicine; on the other hand, it is a source of difficulties in interpretation [2]. Most clinical laboratories standardize the preanalytical phase by controlling and monitoring the preanalytical variables (e.g., specimen collection and handling), reducing the magnitude of the errors or inaccuracies in the obtained laboratory test results associated with these parameters. The scale of inaccuracy of the preanalytical variables as well as their influence on the results of laboratory tests remain significant [8]
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