The white blood cell differential assesses the ability of the body to respond to and fight infection. It also detects the severity of allergic reactions, parasitic and other types of infection, and drug reactions. It can also identify some types of leukaemia or lymphoma.
The results indicate the percentage 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 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 viral infection, leukaemia, lymphoma, or radiation therapy. Decreased lymphocyte levels are common in later life but can also indicate steroid mediation, 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.
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.