Which statement describes hematocrit more accurately?

Which statement describes hematocrit more accurately?

• A. The percentage measures the volume of plasma
• B. It measures the percentage of packed white blood cells
• C. It measures the percentage of red blood cells in whole blood
• D. Normal hematocrit values for men are 60%-70%

Answer: (C)

Hematocrit is the fraction of blood that is made up by red blood cells. It’s determined by spinning a blood sample so the components separate: plasma on top, a small buffy coat of white cells and platelets, and a bottom layer of packed red cells. The hematocrit is the percentage of the total blood volume that the red cell layer represents. That’s why the statement describing hematocrit as the percentage of red blood cells in whole blood is the accurate one. The other ideas mix up what hematocrit measures: plasma volume would be the liquid component’s share, not the cellular portion; white blood cells don’t define hematocrit (their portion is part of the buffy coat); and normal values for men are not as high as 60–70%—that range would indicate an abnormally high red cell mass.

Hematocrit is the fraction of blood that is made up by red blood cells. It’s determined by spinning a blood sample so the components separate: plasma on top, a small buffy coat of white cells and platelets, and a bottom layer of packed red cells. The hematocrit is the percentage of the total blood volume that the red cell layer represents. That’s why the statement describing hematocrit as the percentage of red blood cells in whole blood is the accurate one.

The other ideas mix up what hematocrit measures: plasma volume would be the liquid component’s share, not the cellular portion; white blood cells don’t define hematocrit (their portion is part of the buffy coat); and normal values for men are not as high as 60–70%—that range would indicate an abnormally high red cell mass.