What is the purpose of using a hematocrit tube?

Using a hematocrit tube serves the specific purpose of measuring the percentage of red blood cells (RBCs) in a blood sample. This measurement is important because it helps in assessing the proportion of blood that is composed of RBCs, which is critical for diagnosing various conditions such as anemia, polycythemia, and other blood disorders.

The hematocrit test, performed using a specially designed tube, involves centrifuging the blood sample; this process separates the components of blood according to their density. After centrifugation, the red blood cells will settle at the bottom of the tube, while the plasma will remain at the top. The volume of the RBC layer compared to the total volume of blood enables healthcare providers to calculate the hematocrit value, which is expressed as a percentage.

In contrast, the other options relate to different types of tests or measurements that do not utilize a hematocrit tube. For example, measuring the volume of plasma, determining white blood cell counts, or analyzing blood glucose levels each require different techniques or tools that are not applicable to the functionality of a hematocrit tube. Thus, B is the most accurate answer regarding the purpose of a hematocrit tube.