Sickle Cell Test

Written by Colleen M. Story | Published on July 25, 2012
Medically Reviewed by George Krucik, MD

What is a Sickle Cell Test?

A sickle cell test is a simple blood test used to determine whether or not you have sickle cell disease or sickle cell trait. Sickle cell disease (SCD) is a group of inherited red blood cell disorders. People who have this disease have red blood cells that are shaped abnormally. Instead of looking like doughnuts, which normal red blood cells do, they are shaped like a crescent moon, or a C-shaped farm tool known as a sickle.

The cells often become hard and sticky, which can increase the risk of blood clots. They also tend to die off early, and this causes a constant shortage of red blood cells.

People with sickle cell trait are genetic "carriers" of sickle cell disease. They have no symptoms of sickle cell disease and cannot develop the disease, but they may be able to pass it on to their children. Those with the trait may have a higher risk of some other complications, including unexpected exercise-related death.

This test is part of the routine screenings performed after a baby is born, but it may also be used on older children and adults when needed.

Who Needs a Sickle Cell Test?

Newborns are regularly screened for sickle cell disease soon after birth. Testing early helps ensure that infants with sickle cell get the proper treatment right away, to protect their health. Since children with sickle cell disease may be more vulnerable to serious infections within weeks of birth, early diagnosis is key.

Immigrants who haven’t been tested abroad, or children who move from one state to another and have not been tested, may also go through a sickle cell test just as a precaution. (Harvard University, 2002) Finally, any individuals displaying symptoms of the disease may need to get tested.

According to the Centers for Disease Control and Prevention (CDC), SCD affects an estimated 80,000 to 100,000 Americans. (CDC) The disease causes the following symptoms:

  • anemia (which causes fatigue)
  • paleness and shortness of breath
  • yellowing of the skin and eyes
  • periodic episodes of pain (caused by blocked blood flow)
  • hand-foot syndrome (swollen hands and feet)
  • frequent infections
  • delayed growth
  • vision problems

What Happens During a Sickle Cell Test?

For a sickle cell test, you will need to provide your doctor with a blood sample. Your healthcare provider will normally take this blood from one of your veins in a regular blood test.

An elastic band will be placed around your upper arm to make the vein swell with blood. Then, a needle will be gently inserted into the vein. The blood will naturally flow out into the tube that’s attached to the needle. When there is enough blood for the test, the healthcare professional will take the needle out and cover the puncture wound with a bandage.

When the test is performed in infants or very young children, the healthcare provider may use a sharp tool called a lancet to puncture skin on the heel or finger, and collect blood onto a slide or test strip.

Are Any Complications Associated with the Test?

As the sickle cell test is a normal blood test, complications are extremely rare. You may feel a little lightheaded or dizzy after the test, but these symptoms will go away with time and if you sit down for a few minutes. Eating a snack may also help.

There is also a rare chance that the puncture wound could become infected, but the alcohol swab used prior to the test normally prevents this. If you develop a bruise at the injection site, apply warm compresses and it will heal in time.

What Do the Test Results Mean?

A laboratory technician examining your blood sample will be looking for an abnormal form of hemoglobin called hemoglobin S. Regular hemoglobin is a protein carried by red blood cells that picks up oxygen in the lungs and delivers it to other tissues and organs throughout your body.

Like all proteins, the "blueprint" for hemoglobin exists in our DNA, the material that makes up our genes. If one of the genes is altered, however, or has mutated, it can change how the hemoglobin behaves. Such mutated or abnormal hemoglobin can create red blood cells that are sickle-shaped, leading to sickle cell disease.

A sickle cell test looks only for the presence of hemoglobin S, which causes sickle cell disease. A negative test is normal, and means that your hemoglobin is normal. A positive test result may mean that you have either sickle cell trait or sickle cell disease.

If the test is positive, your doctor will probably order a second test called hemoglobin electrophoresis, which will help determine which condition you have. If the test shows that you have two abnormal hemoglobin genes, you will likely be diagnosed as having sickle cell disease. If the test shows you have only one of these abnormal genes and no symptoms, you will likely be diagnosed as having the sickle cell trait.

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