Osmotic fragility

Osmotic fragility is a test to detect whether red blood cells are more likely to break down.

Why is the Test 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.

How is the Test 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.

Preparation for the Test

No special preparation is necessary for this test.

How will the Test 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.

Osmotic fragility 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)

Normal Results for Osmotic fragility

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

Review Date: 3/21/2010
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.

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