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Stability of plasma glucose during storage
M L Clark1, S M Humphreys, K N Frayn
1Sheikh Rashid Diabetes Unit, Radcliffe Infirmary, Oxford, UK.
Annals of Clinical Biochemistry
|July 1, 1990
Summary
Plasma glucose levels decrease during storage, with a typical 10% loss observed over months. This glucose degradation occurs regardless of the analytical method used and is not prevented by fluoride.
Area of Science:
- Biochemistry
- Clinical Chemistry
- Laboratory Medicine
Background:
- Accurate measurement of plasma glucose is critical for metabolic research and clinical diagnostics.
- Variability in sample handling and storage can potentially affect analyte concentrations.
- Previous observations suggested glucose instability, but comprehensive data across different methods and storage conditions were lacking.
Purpose of the Study:
- To investigate the phenomenon of plasma glucose decrease during frozen storage.
- To determine if this glucose loss is dependent on the analytical method employed.
- To assess the impact of repeated freeze-thaw cycles and the presence of fluoride on glucose stability.
Main Methods:
- Plasma samples were analyzed for glucose using two distinct methods: a glucose oxidase-based analyzer (Beckman Glucose Analyser 2) and a hexokinase-based technique on a centrifugal analyzer.
- Samples were stored frozen for extended periods (up to 14 months).
- Additional experiments involved repeated freeze-thaw cycles and storage with fluoride, as well as analysis of frozen perchloric acid extracts of blood.
Main Results:
- A consistent decrease in plasma glucose concentration was observed during frozen storage, typically around 10% over several months.
- This glucose loss was independent of the analytical method used (glucose oxidase vs. hexokinase).
- Repeated freezing and thawing did not significantly increase glucose loss compared to single thawing, and fluoride did not prevent the observed decrease. Glucose was also lost from frozen blood extracts.
Conclusions:
- Variable loss of glucose during plasma storage is a significant factor that can complicate the interpretation of metabolic research findings.
- The observed glucose degradation is a pre-analytical issue, occurring before or during sample analysis, and is not method-dependent.
- Researchers should be aware of this glucose instability when designing studies involving stored plasma samples to ensure data integrity.