Which CBC parameter directly reflects the oxygen-carrying capacity of blood?

• A. Hemoglobin
• B. Platelet count
• C. WBC
• D. MCV

Answer: (A)

Hemoglobin is the protein in red blood cells that binds and carries oxygen from the lungs to tissues throughout the body. The amount of hemoglobin in the blood directly determines how much oxygen can be transported, so hemoglobin concentration is the CBC parameter that directly reflects oxygen-carrying capacity. Platelets are involved in clotting, and white blood cells in immune defense, neither of which measure oxygen transport. MCV indicates the size of red blood cells, not how much oxygen they can carry. So the best answer is the hemoglobin level.