Which measurement determines the percentage of blood volume occupied by red blood cells?

• A. Hematocrit
• B. Mean corpuscular volume
• C. Packed cell volume
• D. Mean corpuscular hemoglobin

Answer: (C)

The main idea is the proportion of blood that is made up of red blood cells. This is described by the hematocrit, and in veterinary practice it’s commonly called packed cell volume (PCV). You determine it by centrifuging blood in a capillary tube so the red cells pack at the bottom and plasma sits above; then you read the height of the red cell column as a percentage of the total column. That percentage is the PCV, which equals the hematocrit.

Mean corpuscular volume gives the average size of individual red blood cells, not how much of the blood’s volume they occupy, and mean corpuscular hemoglobin reflects the amount of hemoglobin per cell, not the overall volume fraction.