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Basophil (close-up)
Basophil (close-up)


Formed elements of blood
Formed elements of blood


Blood differential

Definition:

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.

See also:



Alternative Names:

Differential; White blood cell differential count



How the Test is Performed:

The health care provider will take blood from your vein. The blood collects into an airtight container.

In infants or a young child, blood will be taken from a heel stick or finger stick. The blood is collected in a small glass tube or onto a slide or test strip.

Cotton or a bandage may be applied to stop any bleeding.

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 the 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, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.



Why the Test is Performed:

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



Normal Results:
  • 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:

A decreased percentage of neutrophils may be due to:

An increased percentage of lymphocytes may be due to:

A decreased percentage of lymphocytes may be due to:

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's disease
  • Allergic reaction
  • Cancer
  • Collagen vascular disease
  • Hypereosinophilic syndromes
  • Parasitic infection

An increased percentage of basophils may be due to:

  • After splenectomy
  • Allergic reaction
  • 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 light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)


References:

Bain BJ. The peripheral blood smear. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 160.

Berliner N. Leukopenia and leukocytosis. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 170.




Review Date: 2/2/2013
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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