Which of the following hematology test results is expressed as a percentage?

• A. Mean corpuscular volume
• B. Platelet count
• C. Mean corpuscular hemoglobin concentration
• D. Packed cell volume

Answer: (D)

Packed cell volume is the percentage of blood that is made up of red blood cells. It’s determined by centrifuging the blood and comparing the height of the packed red cell layer to the total sample height; the ratio, multiplied by 100, gives the percent. This percentage reflects how much of the blood’s volume is occupied by cells, which is why it’s reported as a percent value.

Mean corpuscular volume measures the average size of red blood cells and is reported in femtoliters, not a percentage. Platelet count is a cell count per volume (for example, x10^9/L or per microliter), not a percentage. Mean corpuscular hemoglobin concentration represents how concentrated hemoglobin is inside red cells and is typically reported in g/dL.