A blood smear is a blood test that gives information about the number and shape of blood cells.
A blood sample is needed.
The blood sample is sent to a lab. There, the lab technician looks at it under a microscope. Or, the blood may be examined by an automated machine. The smear shows the number and kinds of white blood cells (differential), abnormally-shaped blood cells, and gives a rough estimate of white blood cell and platelet counts.
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 a slight bruise. This soon goes away.
This test may be done as part of a general health exam to help diagnose many illnesses. Or, your doctor may order this test if you have signs of any of the following disorders: Any known or suspected blood disorder
Red blood cells normally are the same in size and color and have a lighter-colored area in the center. The blood smear is considered normal if there is:
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
Abnormal results mean there is an abnormality in the size, shape, color, or coating of the red blood cells (RBCs).
Some abnormalities may be graded on a 4-point scale:
Presence of target cells may be due to:
Presence of sphere-shaped cells (spherocytes) may be due to:
Presence of fragmented cells (schistocytes) may be due to:
Presence of a type of immature red blood cell called a normoblast may be due to:
The presence of burr cells (echinocytes) may indicate:
The presence of spur cells (acanthocytes) may indicate:
The presence of teardrop-shaped cells may indicate:
The presence of Howell-Jolly bodies may indicate:
The presence of Heinz bodies may indicate:
The presence of slightly immature red blood cells (reticulocytes) may indicate:
The presence of basophilic stippling may indicate:
The presence of sickle cells may indicate sickle cell anemia.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Bain BJ. The peripheral blood smear. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 160.
Vajpayee N, Graham SS, Bern 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.
Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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