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Blood differential test

Differential; White blood cell differential count

 

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 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.

 

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.

 

Normal Results

 

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%

 

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.

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

 

Risks

 

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)

 

 

References

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 30.

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  • Basophil (close-up)

    Basophil (close-up)

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  • Formed elements of blood

    Formed elements of blood

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    • Basophil (close-up)

      Basophil (close-up)

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    • Formed elements of blood

      Formed elements of blood

      illustration

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          Review Date: 1/27/2015

          Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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