Blood differential test
The blood differential test measures the percentage of each type of white blood cell (WBC) that you have in your blood. It also reveals if there are any abnormal or immature cells.
How the Test is Performed
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 special machine 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.
How to Prepare for the Test
No special preparation is necessary.
How the Test will Feel
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.
Why the Test is Performed
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.
Anemia
Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. Different type...
Leukemia
Leukemia is a type of blood cancer that begins in the bone marrow. Bone marrow is the soft tissue in the center of the bones, where blood cells are ...
Normal Results
The different types of white blood cells are given as a percentage of all white cells:
- 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%
What Abnormal Results Mean
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. Abnormal or immature white blood cells may indicate leukemia or bone marrow invasion by cancer or infection.
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
- Inflammation
- Acute stress
- Eclampsia (seizures or coma in a pregnant woman)
- Gout (type of arthritis due to uric acid buildup in the blood)
- Acute or chronic forms of leukemia
- Myeloproliferative diseases
- Rheumatoid arthritis
- Rheumatic fever (disease due to an infection with group A streptococcus bacteria)
- Thyroiditis (a thyroid disease)
- Trauma
- Cigarette smoking
A decreased percentage of neutrophils may be due to:
- Aplastic anemia
- Chemotherapy
Chemotherapy
The term chemotherapy is used to describe cancer-killing drugs. Chemotherapy may be used to:Cure the cancerShrink the cancerPrevent the cancer from ...
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- Radiation therapy or exposure
Radiation therapy
Radiation therapy uses high-powered radiation (such as x-rays or gamma rays), particles, or radioactive seeds to kill cancer cells.
ImageRead Article Now Book Mark Article - Viral infection
- Widespread severe bacterial infection (sepsis)
An increased percentage of lymphocytes may be due to:
- Chronic bacterial infection
- Infectious hepatitis (liver swelling and inflammation from bacteria or viruses)
- Infectious mononucleosis, or mono (viral infection that causes fever, sore throat, and swollen lymph glands)
- Tuberculosis
- Lymphocytic leukemia (a type of blood cancer)
Lymphocytic leukemia
Acute lymphoblastic leukemia (ALL) is a fast-growing cancer of a type of white blood cells called lymphocytes. ALL occurs when the bone marrow produ...
ImageRead Article Now Book Mark Article - Multiple myeloma (a type of blood cancer)
Multiple myeloma
Multiple myeloma is a blood cancer that starts in the plasma cells in the bone marrow. Bone marrow is the soft, spongy tissue found inside most bone...
ImageRead Article Now Book Mark Article - Viral infection (such as mumps or measles)
A decreased percentage of lymphocytes may be due to:
- Chemotherapy
Chemotherapy
The term chemotherapy is used to describe cancer-killing drugs. Chemotherapy may be used to:Cure the cancerShrink the cancerPrevent the cancer from ...
ImageRead Article Now Book Mark Article - HIV/AIDS infection
- Leukemia
- Radiation therapy or exposure
Radiation therapy
Radiation therapy uses high-powered radiation (such as x-rays or gamma rays), particles, or radioactive seeds to kill cancer cells.
ImageRead Article Now Book Mark Article - Sepsis (severe, inflammatory response to bacteria or other germs)
- Steroid use
An increased percentage of monocytes may be due to:
- Chronic inflammatory disease
- Leukemia
- Parasitic infection
- Tuberculosis, or TB (bacterial infection that involves the lungs)
- Viral infection (for example, infectious mononucleosis, mumps, or measles)
An increased percentage of eosinophils may be due to:
- Addison disease (adrenal glands do not produce enough hormones)
- Allergic reaction
- Cancer
Cancer
Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.
Read Article Now Book Mark Article - Chronic myelogenous leukemia
Chronic myelogenous leukemia
Chronic myelogenous leukemia (CML) is cancer that starts inside the bone marrow. This is the soft tissue in the center of bones that helps form all ...
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- Hypereosinophilic syndromes
- Parasitic infection
An increased percentage of basophils may be due to:
- After splenectomy
- Allergic reaction
- Chronic myelogenous leukemia (a type of bone marrow cancer)
Chronic myelogenous leukemia
Chronic myelogenous leukemia (CML) is cancer that starts inside the bone marrow. This is the soft tissue in the center of bones that helps form all ...
ImageRead Article Now Book Mark Article - Collagen vascular disease
- Myeloproliferative diseases (group of bone marrow diseases)
- Chickenpox
A decreased percentage of basophils may be due to:
- Acute infection
- Cancer
- Severe injury
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person 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
- Multiple punctures to locate veins
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Reviewed By
Mark Levin, MD, Hematologist and Oncologist, Monsey, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Bain BJ. The peripheral blood smear. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 148.
Nasr MR, Hutchison RE. Leukocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 34.
