Short-term and long-term stability of antioxidant species in plasma samples

Introduction: Reactive oxygen species and other oxidants can target various biological macromolecules and the organism responds with internal antioxidant systems. The antioxidant capacity in biological systems can be measured by tests like Plasma Antioxidant Test (PAT test), which evaluates the entire antioxidant capacity rather than just one analyte and is not affected by antioxidant enzymatic activity. Stability of antioxidant species in biological samples is crucial data for reliable measurements since preanalytical degradation of the analyte can affect results significantly. We examined short-term stability of antioxidant species in plasma under different temperature conditions and long-term stability of the analyte in frozen plasma samples. Methods: Antioxidant species in plasma measured using PAT test, which is designed to assess the antioxidant capacity of plasma by measuring the total iron-reducing capacity in a sample. Results and Conclusions: Storage of plasma samples for up to 30 hours at 2-8 °C or even at room temperature did not cause substantial bias to the measurement. The influence on results did not exceed the repeatability of the method. Long-term storage of plasma samples up to 12 months at –30 °C did not have a significant impact on results even if the samples were thawed and frozen again.