Blood differential test

Differential; White blood cell differential count

A blood sample is needed.

A laboratory specialist takes a drop of blood from your sample and smears it onto a glass slide. The smear is stained with a special dye, which helps tell the difference between various types of white blood cells.

Five types of white blood cells, also called leukocytes, normally appear in the blood:

• Neutrophils
• Lymphocytes (B cells and T cells)
• Monocytes
• Eosinophils
• Basophils

A specially designed machine or a health care provider counts the number of each type of cell. The test shows if the number of cells are in proper proportion with one another, and if there is more or less of one cell type.

No special preparation is necessary.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

This test is done to diagnose an infection, anemia, or leukemia. It may also be used to monitor one of these conditions, or to see if treatment is working.

The different types of white blood cells are given as a percentage:

• Neutrophils: 40 to 60%
• Lymphocytes: 20 to 40%
• Monocytes: 2 to 8%
• Eosinophils: 1 to 4%
• Basophils: 0.5 to 1%
• Band (young neutrophil): 0 to 3%

Any infection or acute stress increases your number of white blood cells. High white blood cell counts may be due to inflammation, an immune response, or blood diseases such as leukemia.

It is important to realize that an abnormal increase in one type of white blood cell can cause a decrease in the percentage of other types of white blood cells.

An increased percentage of neutrophils may be due to:

• Acute infection
• Acute stress
• Eclampsia
• Gout
• Myelocytic leukemia
• Rheumatoid arthritis
• Rheumatic fever
• Thyroiditis
• Trauma

A decreased percentage of neutrophils may be due to:

• Aplastic anemia
• Chemotherapy
• Influenza (flu)
• Radiation therapy or exposure
• Viral infection
• Widespread severe bacterial infection

An increased percentage of lymphocytes may be due to:

• Chronic bacterial infection
• Infectious hepatitis
• Infectious mononucleosis
• Lymphocytic leukemia
• Multiple myeloma
• Viral infection (such as mumps or measles)

A decreased percentage of lymphocytes may be due to:

• Chemotherapy
• HIV infection
• Leukemia
• Radiation therapy or exposure
• Sepsis
• Steroid use

An increased percentage of monocytes may be due to:

• Chronic inflammatory disease
• Leukemia
• Parasitic infection
• Tuberculosis
• Viral infection (for example, infectious mononucleosis, mumps, measles)

An increased percentage of eosinophils may be due to:

• Addison disease
• Allergic reaction
• Cancer
• Chronic myelogenous leukemia
• Collagen vascular disease
• Hypereosinophilic syndromes
• Parasitic infection

An increased percentage of basophils may be due to:

• After splenectomy
• Allergic reaction
• Chronic myelogenous leukemia
• Collagen vascular disease
• Myeloproliferative disease
• Varicella infection

A decreased percentage of basophils may be due to:

• Acute infection
• Cancer
• Severe injury

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)