To diagnose an illness affecting your immune system, such as an infection, inflammatory illness, immune deficiency, or tumour such as leukaemia or lymphoma
White Blood Cell Differential Count
A blood sample taken from a vein in your arm or by a finger-prick (children and adults) or heel-prick (infants)
There are five types of white blood cells, each with different functions: neutrophils, lymphocytes, monocytes, eosinophils and basophils. The differential reveals if these cells are present in normal proportion to one another, if one cell type is increased or decreased, or if immature or abnormal cells are present. This information is helpful in diagnosing specific types of illnesses that affect the immune system.
White blood cells are made in your bone marrow or lymphoid system. They protect your body against infection and aid your immune system. If an infection develops, white blood cells attack and destroy the microorganism causing the infection.
How is the sample collected for testing?
The test is performed on a blood sample taken from a vein in the arm or from a finger-prick (for children and adults) or heel-prick (for infants).
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
The white blood cell differential assesses the ability of the body to respond to and fight infection, including HIV-AIDS. It can detect the severity of allergic and drug reactions, parasitic and other types of infection. It can also identify some types of leukaemia and lymphoma, and detect other diseases affecting the bone marrow.
When is it requested?
What does the test result mean?
The results indicate the relative percentage and actual numbers of each type of white blood cell that is present.
Neutrophils can increase in response to bacterial infection, inflammatory disease, steroid medication, or more rarely leukaemia. Decreased neutrophil levels may be the result of severe infection, liver disease, enlarged spleens or other conditions, such as responses to various medications or chemotherapy.
Eosinophils can increase in response to allergic disorders, inflammation of the skin, and parasitic infections. They can also occur in response to some infections or to various bone marrow malignancies.
Basophils can increase in cases of leukaemia, long-standing inflammation, the presence of a hypersensitivity reaction to food, or radiation therapy.
Lymphocytes can increase in cases of bacterial or especially viral infection, leukaemia, lymphoma and in people with underactive or absent spleens. Decreased lymphocyte levels are common in later life but can also be due to steroid medication, stress, lupus, and HIV infection.
Monocyte levels can increase in certain leukaemias, in response to infection of all kinds as well as to inflammatory disorders. Decreased monocyte levels can indicate bone marrow injury or failure and some forms of leukaemia - especially "hairy cell leukaemia".
Is there anything else I should know?
Eating, physical activity, and stress may alter white blood cell differential values.
Long-term exposure to toxic chemicals (for example some solvents, petroleum products and insecticides) can increase the risk of an abnormal differential as can smoking.
What are the individual functions of each type of white blood cell?
- Neutrophils, the most abundant white blood cells, are 'phagocytes' - that is, they 'eat' foreign organisms and kill them with internal poisons. They are important for fighting bacterial and fungal infections.
- Lymphocytes are more specifically acting killers of infection and regulate the immune response. B-lymphocytes produce antibodies. T-lymphocytes act as messenger cells, directing the immune response. T-cells and NK-cells can also act directly to kill specific infective organisms. Lymphocytes are the cells which 'remember' previous infections and guard against re-infection with the same organism. They are active against all types of infection including bacteria, fungi, parasites and viruses. When they malfunction they also have a role in allergy and in autoimmune diseases such as rheumatoid arthritis and lupus.
- Monocytes are phagocytes, like neutrophils, active against bacteria, fungi, and tuberculosis.
- Eosinophils increase during allergic attacks and some parasitic infestations.
- Basophils control inflammation and damage to the body. They increase in some blood diseases and in some inflammatory bowel diseases.
What are other names for neutrophils that might appear on a lab report?
Neutrophils are also known as granulocytes, polymorphs, and PMNs.