Variability of alpha-tocopherol values associated with procurement, storage, and freezing of equine serum and plasma samples.

This research investigates the potential impact of various factors related to the collection, transport and storage of equine blood samples on measurements of alpha-tocopherol, a compound implicated in equine degenerative myeloencephalopathy.

Impact of Various Factors on Alpha-Tocopherol Concentration

• The study considered variables that may be introduced while procuring, transporting, or storing equine blood samples and evaluated their effects on alpha-tocopherol concentration. Variables considered included temperature, light, exposure to the rubber stopper of the evacuated blood collection tube, hemolysis, duration of freezing time, with and without nitrogen blanketing, and repeated freeze/thaw cycles.
• Of these, the study found that hemolysis caused the most significant change in the alpha-tocopherol concentration. The impact of hemolysis was measured using high-performance liquid chromatography. Hemolysis, the breakdown of red blood cells, resulted in a mean reduction of 33% in serum alpha-tocopherol values.

Storage Time & Conditions and Alpha-Tocopherol Levels

• Significant but lesser changes (approximately 10% decrease) in serum alpha-tocopherol values were observed when refrigerated blood was left in contact with the red rubber stopper of the blood collection tube for 72 hours. An approximate 5% increase was observed when blood was stored at room temperature (20 to 25 C) for the same duration.
• Regression in alpha-tocopherol values was also seen in heparinized plasma with repeated freeze/thaw cycles. By the third thawing cycle, a significant 3% decrease was noted.
• The effects of freezer storage on alpha-tocopherol levels were also evaluated. A slight reduction of 2% was found in serum alpha-tocopherol values post a 3-month freezer storage period without nitrogen blanketing. By contrast, serum stored for the same period with nitrogen blanketing showed no change.
• However, when the serum was stored in a freezer at -16 C under nitroge blanekting for 6 months, a significant decrease of 10.3% in alpha-tocopherol values was reported.

Conclusion

• Overall, these results highlight the importance of considering various external variables during the procurement, transport and storage of blood samples, particularly in research relating to equine degenerative myeloencephalopathy.