A complete blood count (CBC) is a test often used in evaluating individuals for various diseases. Included in the CBC is the leukocyte differential, also called white blood cell (WBC) differential, which counts the number of the types of WBCs present in a blood sample. The types of WBCs include the neutrophils, the eosinophils, the basophils, the lymphocytes, and the monocytes. These cells are mostly produced in the bone marrow, the fatty tissues found in the large bones. Information about an increase or decrease in the number of any of these cells can help physicians diagnose and monitor their patients' response to treatment.
The types of WBCs being counted in the leukocyte differential count have certain specific functions. Neutrophils help the body fight infections caused by bacteria and fungi. When there is an increase in the number of neutrophils, bacterial infections are usually suspected. A decrease often reveals severe infection, or can also be due to the side effects of chemotherapy, a cancer treatment. Eosinophils are WBCs that often increase in cases of parasitic infections and allergies.
Lymphocytes are important in the production of antibodies, cells that fight anything foreign that enters the body. An increase in lymphocytes is often an indication of virus infection, bone marrow disorders, and leukemia. A decrease in lymphocytes are frequently seen in individuals with immune system disorders such as lupus. Lupus is a disease in which immune system cells attack other cells in the body. The numbers of monocytes and basophils in the leukocyte differential are also increased in some cases of leukemia.
During the test, a phlebotomist, an individuals trained to take blood samples, usually extracts blood from the vein of the patient. Some patients may feel a little pain or discomfort during the process. No preparations are generally needed before the leukocyte differential count is performed. It is, however, recommended that patients inform their physician if they are taking some medications, as some drugs may influence the leukocyte differential count. For instance, using steroids for a long time may lead to an abnormal result.
Some risks associated with the process of taking a blood sample include bleeding and infection from the wound site. There are also a few patients who feel light-headed during and after the procedure. A hematoma, which is the accumulation of blood in the skin, may also develop.