What is the term for a blood test that counts the total number of white blood cells?

The term for a blood test that counts the total number of white blood cells is known as the leukocyte count. White blood cells, or leukocytes, play a crucial role in the body's immune response, helping to fight off infections and other diseases. The leukocyte count is an important diagnostic tool used to assess a person's immune status and can indicate the presence of infection, inflammation, or other medical conditions.

In contrast, hematocrit measures the proportion of blood volume that is occupied by red blood cells, which is different from counting white blood cells. The platelet count focuses on the number of platelets present in the blood, vital for clotting, while the hemoglobin test measures the protein in red blood cells that carries oxygen. Therefore, the leukocyte count is specific to white blood cells, making it the correct answer for this question.