Effect of repeated freeze-thaw cycles on routine plasma biochemical constituents in canine plasma

Background: The effect of repeated freeze-thaw cycles on plasma constituents has not been assessed in dogs, although such a procedure is not uncommon to use in routine laboratory practice. Objective: To assess the effect of freeze-thaw cycles on routine plasma constituents in healthy dogs. Methods: Six healthy adult dogs were used. Blood was sampled and placed in heparinized tubes. After centrifugation, plasma was separated into 5 aliquots. One aliquot was considered as the reference aliquot and used immediately for the assay of all of the biochemical constituents. All of the other aliquots; were stored at -20 degrees C. Three aliquots underwent 1, 2, or 3 freeze-thaw cycles during a 1- to 3-day period. The last aliquot remained at -20 degrees C throughout the study and was thawed on the third day. The following biochemical constituents were assayed: glucose, urea, creatinine, total proteins, sodium, potassium, chloride, calcium, phosphates, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), and alkaline phosphatase (ALP). Results: No clinically relevant change was observed between the different aliquots for all of the constituents. Conclusion: Repeated freeze-thaw cycles do not cause changes in the biochemical constituents studied in canine plasma.