A simple blood test often is all that is needed for healthcare providers to make a diagnosis of sickle cell disease or SCD — a group of inherited conditions in which red blood cells acquire an abnormal sickle-like shape and die prematurely.
The disorder often results in anemia and circulatory problems, and people with sickle cell disease can pass it on to their biological children.
Sickle cell disease is caused by a mutation in the HBB gene that leads to the production of abnormal hemoglobin — the protein that carries oxygen in red blood cells. Abnormal hemoglobin molecules cause red blood cells to become misshapen, rigid, and sticky. This, in turn, makes it harder for them to move through small blood vessels, impairing circulation and causing blockages.
Generally, all individuals have two copies of a given gene, one inherited from each parent. People who inherit only one mutated copy of the HBB gene usually do not show any symptoms of sickle cell disease, and are said to have the sickle cell trait. However, those with two faulty copies of the gene will develop sickle cell disease.
Several screening tests can be performed to identify the presence of sickle cell disease. Screening for SCD is done with a simple blood test that detects the presence of abnormal hemoglobin proteins. Those who are concerned about sickle cell trait also can get tested.
Patients with sickle cell trait or parents of newborn babies diagnosed with sickle cell disease or sickle cell trait often are referred to genetic counseling to learn more about their specific diagnosis.
Such counseling also can help prospective parents determine the probability of having children who will inherit the disease, so they can make fully informed reproductive decisions.
Prenatal and newborn screening
For expectant parents with a history of sickle cell disease, a test for the disorder may be performed before birth using a small sample of amniotic fluid — the liquid that surrounds the unborn baby — or the placenta. These prenatal tests screen for the mutated HBB gene, rather than abnormal hemoglobin proteins.
In many countries, including the U.S., a blood test looking for abnormal hemoglobin proteins is part of routine newborn screening programs.
Patients who test positive for abnormal hemoglobin do not necessarily have sickle cell disease and may only have the sickle cell trait. For this reason, further testing is needed to make a definitive diagnosis. A blood test also may be repeated to rule out a false-positive result.
Several types of sickle cell disease exist, depending on which type of abnormal hemoglobin the patient’s body makes. As such, a more specific blood test often is used to determine which type of abnormal hemoglobin a patient produces.
Patients diagnosed with sickle cell disease require frequent laboratory tests including blood and urine tests, to monitor possible complications, such as kidney problems or infections.
Due to the accumulation of sickle-shaped red blood cells in the brain’s small blood vessels, people with sickle cell disease are at an increased risk of having a stroke. Estimates indicate that 11% of sickle cell disease patients will have a stroke by the age of 20, and that this risk is highest between ages 2 and 5.
A transcranial Doppler ultrasound or TCD, a painless procedure that uses sound waves to assess blood flow in the brain, can be used to identify narrowed blood vessel sections and determine one’s risk of having a stroke. By being evaluated for the risk of stroke, patients can initiate treatments to reduce that risk, if necessary.
Last updated: Sept. 14, 2021
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