Which of the following statements applies to the preferred use of plasma or serum, rather than whole blood, for glucose determination?

• A. Glucose is more stable in separated plasma or serum.
• B. Specificity for glucose is higher with most methods when plasma or serum is used.
• C. It is convenient to use serum or plasma with automated instruments because whole blood requires mixing immediately before sampling.
• D. All the above.

Answer: (D)

Glucose levels in blood can change after collection because the cells in whole blood continue to metabolize glucose, so the concentration falls if processing is delayed. Separating plasma or serum removes these cells, stopping most glycolysis and stabilizing the glucose level during transport and analysis.

Using plasma or serum also tends to give more reliable results with many glucose methods because the sample matrix is cleaner and there are fewer cellular interferences that can affect the assay’s readout. This often translates into better specificity for glucose and less interference from substances released by cells.

In automated laboratory instruments, handling plasma or serum is straightforward and standardized, whereas whole blood often requires immediate and careful mixing and additional handling to avoid ongoing glycolysis and clotting issues, which can complicate measurement. For these reasons, plasma or serum are generally preferred for glucose determination.

All of these points together explain why plasma or serum is favored in glucose testing.