What component of the CBC provides a measure of the number of red blood cells?

The component of the Complete Blood Count (CBC) that directly measures the number of red blood cells (RBCs) is the RBC count. This value is critical in assessing a patient's overall blood health and oxygen-carrying capacity. An accurate RBC count can help diagnose conditions such as anemia, polycythemia, and other hematological disorders, providing insight into the body's production of red blood cells and their lifespan.

The hematocrit measures the proportion of blood volume that is occupied by red blood cells, which is relevant but not a direct count of the cells themselves. The platelet count measures the number of platelets in the blood, essential for blood clotting, whereas the WBC count assesses the number of white blood cells, which are primarily involved in the immune response. Each of these components serves a unique purpose within the CBC, but when it comes to quantifying the actual number of red blood cells present, the RBC count is the definitive measurement.