Which of the following is the best method of preservation if you are unable to perform a CBC within 1 hour of blood collection?

Which of the following is the best method of preservation if you are unable to perform a CBC within 1 hour of blood collection?

• A. Freeze the sample
• B. Spin down the sample, refrigerate cells, and freeze serum
• C. Add formalin to the sample
• D. Refrigerate the sample

Answer: (D)

Preserving a CBC sample means keeping the intact cells in the blood so that counts and morphology remain accurate. For a CBC, you’re counting and evaluating whole blood cells, so the sample needs to stay as close to its natural state as possible. Refrigerating the sample slows cellular metabolism and prevents rapid changes in cell integrity that occur at room temperature, helping to maintain accurate red and white cell counts and platelets until you can run the test. Freezing whole blood would crush or rupture cells and distort morphology, making the CBC unreliable. Separating serum or plasma and freezing it removes the cells needed for the CBC, and adding a fixative like formalin would fix and alter cells in a way that prevents correct counting. Thus, keeping the sample refrigerated is the best option when processing is delayed. If possible, store at 2–8°C and analyze promptly after thawing.

Preserving a CBC sample means keeping the intact cells in the blood so that counts and morphology remain accurate. For a CBC, you’re counting and evaluating whole blood cells, so the sample needs to stay as close to its natural state as possible.

Refrigerating the sample slows cellular metabolism and prevents rapid changes in cell integrity that occur at room temperature, helping to maintain accurate red and white cell counts and platelets until you can run the test. Freezing whole blood would crush or rupture cells and distort morphology, making the CBC unreliable. Separating serum or plasma and freezing it removes the cells needed for the CBC, and adding a fixative like formalin would fix and alter cells in a way that prevents correct counting. Thus, keeping the sample refrigerated is the best option when processing is delayed. If possible, store at 2–8°C and analyze promptly after thawing.