How the Test is Performed

A blood sample is needed. For information on how this is done, see: Venipuncture

In the laboratory, red blood cells are tested with a solution that makes them swell, in order to determine how fragile they are.

How to Prepare for the Test

No special preparation is necessary for this test.

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 performed to detect hereditary spherocytosis and thalassemia. Hereditary spherocytosis makes red blood cells more fragile than normal. Some red blood cells in patients with thalassemia are more fragile than normal, but a larger number are less fragile than normal.

Normal Results

A negative test is normal.

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.

What Abnormal Results Mean

• Thalassemia
• Hereditary spherocytosis

Risks

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:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Golan DE. Hemolytic anemias: red cell membrane and metabolic defects. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 165.

Gallagher PG, Jarolim P. Red blood cell membrane disorders. In: Hoffman R, Benz EJ, Shattil SS, et al., eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 46.

Update Date: 3/21/2012

Reviewed by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.