Which sample can be frozen and thawed for performing an analytic test at a later time?

Which sample can be frozen and thawed for performing an analytic test at a later time?

• A. Serum for chemistry testing
• B. Feces for a fecal float test
• C. Whole blood for chemistry testing
• D. Whole blood for a CBC

Answer: (A)

Sample stability during freeze-thaw cycles depends on the material being stored. Serum can be separated from clotted blood, aliquoted, and stored frozen; when thawed, most chemistry tests still yield reliable results if you avoid multiple freeze-thaw cycles. The lack of cells in serum means there’s less risk of cellular damage altering the analyte concentrations during storage, making it suitable for later analysis. Whole blood, on the other hand, contains red cells and platelets. Freezing can damage these cells, causing hemolysis or leakage of intracellular components, which skews chemistry values and makes a CBC unreliable after thawing. Feces are typically tested fresh for fecal flotation because freezing can affect parasite eggs or other diagnostic features and alter the accuracy of the test. Therefore, serum is the sample type that can be frozen and thawed for later analytic testing.

Sample stability during freeze-thaw cycles depends on the material being stored. Serum can be separated from clotted blood, aliquoted, and stored frozen; when thawed, most chemistry tests still yield reliable results if you avoid multiple freeze-thaw cycles. The lack of cells in serum means there’s less risk of cellular damage altering the analyte concentrations during storage, making it suitable for later analysis.

Whole blood, on the other hand, contains red cells and platelets. Freezing can damage these cells, causing hemolysis or leakage of intracellular components, which skews chemistry values and makes a CBC unreliable after thawing. Feces are typically tested fresh for fecal flotation because freezing can affect parasite eggs or other diagnostic features and alter the accuracy of the test. Therefore, serum is the sample type that can be frozen and thawed for later analytic testing.