Test Overview
A sickle cell test is a blood test done to check for sickle cell trait or sickle cell disease. Sickle cell disease is an inherited blood disease that causes red blood cells to be deformed (sickle-shaped). The red blood cells deform because they contain an abnormal type of hemoglobin, called hemoglobin S, instead of the normal hemoglobin, called hemoglobin A.
Sickled blood cells are destroyed by the body faster than normal blood cells. This causes anemia. Also, sickled cells can get trapped in blood vessels and reduce or block blood flow. This can damage organs, muscles, and bones and may lead to life-threatening conditions.
The best way to check for sickle cell trait or sickle cell disease is to look at the blood using a method called high-performance liquid chromatography (HPLC). This test identifies which type of hemoglobin is present. To confirm the results of HPLC, a genetic test may be done.
A person inherits two sets of genes (one set from each parent). As a result, a person may have:
- Two sets of genes that make normal hemoglobin (hemoglobin A). These people have normal red blood cells unless they have some other blood disease.
- One set of genes that makes normal hemoglobin (hemoglobin A) and one set that makes hemoglobin S. These people carry the sickle cell trait (and are called "carriers"), but they do not have sickle cell disease. Sickle cell trait is usually a harmless condition.
- Two sets of genes that make hemoglobin S. These people have sickle cell disease. Both parents either carry the sickle cell trait or have the disease. Sickled red blood cells often cause recurring health problems called sickle cell crises.
- One set of genes that makes hemoglobin S and one set that makes some other abnormal type of hemoglobin. Depending on the other type of abnormal hemoglobin, these people may have mild or severe sickle cell disorder.
The United States Preventive Services Task Force recommends that all newborns be tested for sickle cell disease.footnote 1
Why It Is Done
A sickle cell test is done to help diagnose sickle cell disease.
A sickle cell test is also done to screen for sickle cell trait or sickle cell disease. This test may be done for newborns and for people at high risk. Detecting sickle cell trait is important for couples who want to have children and who may be carriers of sickle cell trait.
How To Prepare
Be sure to tell your doctor if you have had a blood transfusion in the past 4 months because it can interfere with the test results.
How It Is Done
Blood sample from a vein
A health professional uses a needle to take a blood sample, usually from the arm.
Blood sample from a heel stick
A heel stick is used to get a blood sample from a baby. The baby's heel is poked, and several drops of blood are collected.
How It Feels
Blood sample from a vein
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
Blood sample from a heel stick
A brief pain, like a sting or a pinch, is usually felt when the lancet punctures the skin. Your baby may feel a little discomfort with the skin puncture.
Risks
Blood sample from a vein
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Blood sample from a heel stick
There is very little risk of a problem from a heel stick. Your baby may get a small bruise at the puncture site.
Results
Sickle cell test footnote 2 Normal: | Normal hemoglobin is present. |
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Abnormal: | Abnormal hemoglobin is present. - In sickle cell trait, more than half of the hemoglobin is normal (hemoglobin A) and less than half is abnormal (hemoglobin S).
- In sickle cell disease, almost all hemoglobin is hemoglobin S with some hemoglobin called hemoglobin F.
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In babies, a sickle cell blood test may be repeated at 6 months old, or a genetic information (DNA) test may be done.
References
Citations
- U.S. Preventive Services Task Force (2007). Screening for sickle cell disease in newborns. Available online: http://www.ahrq.gov/clinic/uspstf/uspshemo.htm.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Credits
Current as of: July 31, 2024
U.S. Preventive Services Task Force (2007). Screening for sickle cell disease in newborns. Available online: http://www.ahrq.gov/clinic/uspstf/uspshemo.htm.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
