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Sickle cell test

Definition

A sickle cell test looks for the abnormal hemoglobin in the blood that causes sickle cell anemia.

Alternative Names

Sickledex; Hgb S test

How the test is performed

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

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 tell if you have abnormal hemoglobin that causes sickle cell disease and sickle cell trait.

In sickle cell disease, a person has two abnormal hemoglobin S genes. A person with sickle cell trait has only one of these abnormal genes and no symptoms, or only mild ones.

This test does not tell the difference between these two conditions. Another test, called hemoglobin electrophoresis , will be done.

Normal Values

A negative test result 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

  • Sickle cell anemia
  • Sickle cell trait

What the risks are

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)

Special considerations

Iron deficiency or blood transfusions within the past 3 months can cause a false negative result.

Encyclopedia content is provided as information only and not intended to replace the advice and instruction from your personal physician.