Blood smear

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Acute lymphocytic leukemia - photomicrograph	Formed elements of blood	Malaria, microscopic view of cellular parasites	Malaria, photomicrograph of cellular parasites
Red blood cells, elliptocytosis	Red blood cells, multiple sickle cells	Red blood cells, normal	Red blood cells, sickle and pappenheimer
Red blood cells, sickle cell	Red blood cells, sickle cells	Red blood cells, spherocytosis	Red blood cells, target cells
Red blood cells, tear-drop shape

This blood test provides information about the number and shape of blood cells by visual inspection.

Peripheral smear

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The blood is examined under a microscope. It may be examined by an automated "calculator," a technologist, a hematologist, or a pathologist. The smear shows the relative number and kinds of white blood cells (differential), abnormalities in the shape of all types of blood cells, and a rough estimate of white cell and platelet counts.

No special preparation is necessary.

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.

This test may be performed as part of a general health examination, to help in the diagnosis of many illnesses, or when an abnormality of any type of blood cell is suspected.

Review Date: 04/15/2005
Reviewed By: Rita Nanda, MD, Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.