Sickle Cell Test

Hemoglobin S Test

Test Overview

A sickle cell test is a blood test done to screen 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 screen for sickle cell trait or sickle cell disease is to examine 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.

Sickle cell disease is an autosomal recessive disease. This means that to have the disease, a person must inherit a gene for the disease from both parents. Each person inherits two genes (one from each parent). As a result, a person may have:

• Two genes that make normal hemoglobin (hemoglobin A). These people have normal red blood cells, unless they have some other disease.
• One gene that makes hemoglobin A and one that makes hemoglobin S. These people carry the sickle cell trait (and are called "a carrier"), but they do not have sickle cell disease. Sickle cell trait is usually a harmless condition.
• Two 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 gene that makes hemoglobin S and one 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.¹

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Author:	Debby Golonka, MPH	Last Updated: December 9, 2008
Medical Review:	Anne C. Poinier, MD - Internal Medicine Martin Steinberg, MD - Hematology
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