Diagnosing Sickle Cell Disease

Specialists at Hassenfeld Children’s Hospital at NYU Langone have extensive experience in diagnosing and treating sickle cell disease. Early diagnosis of this condition is essential to beginning the treatments that can reduce the risk of life-threatening complications, such as severe infections and strokes. With proper treatment, the vast majority of children with sickle cell disease survive into adulthood.

Hemoglobin is a protein in red blood cells that carries oxygen to organs and tissues throughout the body. Hemoglobin also gives red blood cells their characteristic color.

Hemoglobin F is the type of hemoglobin that babies have before and immediately after birth. After birth, most of the hemoglobin F is gradually replaced with another type, called hemoglobin A. In a child with sickle cell disease, hemoglobin F is gradually replaced with hemoglobin S, which gives red blood cells an abnormal shape and texture.

Risk Factors

The most common and most severe form of sickle cell disease is called sickle cell anemia. This occurs when a child inherits two sickle cell gene mutations, one from each parent.

A child who inherits one mutated sickle cell gene and one normal hemoglobin gene makes some hemoglobin S, which is referred to as sickle cell trait. People with sickle cell trait do not have symptoms of sickle cell disease but can pass along the gene to their children.

Sickle cell gene mutations are most common among people whose families came from Mediterranean countries, sub-Saharan Africa, and certain areas of India.

Symptoms and Complications

In general, infants with sickle cell disease are healthy. However, beginning at around six months of age, the accumulation of abnormal red blood cells starts to cause problems. Because of their abnormal shape and texture, sickle cells can narrow blood vessels that supply blood and oxygen to the limbs and organs, causing a sudden, painful episode, sometimes called a sickle cell crisis. These episodes occur more frequently in children who are dehydrated or have an injury, which causes blood cells to become further deformed.

By the time a baby is about six months old, the spleen—a spongy organ in the abdomen that filters bacteria and other harmful substances from the blood—may become suddenly engorged with abnormal blood cells, preventing it from functioning properly. This condition increases the risk of a life-threatening blood infection known as sepsis.

The risk of infections, including severe respiratory infections, continues throughout childhood and into adulthood. A major contributing factor for this ongoing risk is damage to the spleen, causing the organ to shrink and lose its function in early childhood.

Sickle cells have a shorter lifespan than normal red blood cells. As a result, children with sickle cell disease develop anemia, a lower-than-normal level of red blood cells. Anemia contributes to a delay in a child’s growth and the late onset of puberty.

Children with sickle cell disease may have other complications, such as the development of gallstones, which are made of substances released after red blood cells die.

Trapped blood cells or infection in the lungs can cause acute chest syndrome. Symptoms of acute chest syndrome include cough, chest pain, and shortness of breath. Children with acute chest syndrome may develop asthma, although the exact reason for this is unknown. Although less common, sickle cells can damage the brain’s blood vessels, causing a stroke.

Children who have one or more strokes, large or small, may experience brain damage, which can lead to paralysis, learning disorders, developmental delays, and behavioral conditions, such as attention deficit hyperactivity disorder (ADHD). Eventually, sickle cell disease can damage other vital organs, including the bones, liver, lungs, and kidneys.

Prenatal Genetic Tests

Our doctors offer prenatal genetic tests, such as amniocentesis or chorionic villus sampling, for parents who are known carriers of the sickle cell gene mutation or have a family history of the condition. If you and your partner have a family history of sickle cell disease and you’re unsure about whether or not you carry the mutation, you may also consider genetic testing.

Amniocentesis, usually performed in the second trimester of pregnancy, looks for the abnormal genes in a small sample of the amniotic fluid that surrounds the baby while he or she is in the womb.

Chorionic villus sampling can be performed during the first trimester of pregnancy. With this procedure, a needle is used to remove a small amount of tissue from the placenta—a temporary organ that carries oxygen and nutrients from mother to baby. The tissue is analyzed for the presence of the abnormal gene.

NYU Langone genetic counselors can help you understand the results of these tests.

Blood Tests

A second blood test is needed to confirm a diagnosis of sickle cell disease in babies with a positive newborn screening test result.

Unlike the newborn screening test, which identifies hemoglobin S in blood, this test can determine whether your baby has more hemoglobin S than hemoglobin A. A positive test result means your baby has sickle cell disease. This blood test also measures the total number of red blood cells.

Following confirmation of sickle cell disease, our doctors begin treating infants with sickle cell disease with daily penicillin to prevent infections.

Physical Exam

After a blood test confirms sickle cell disease, your child’s doctor performs a physical examination to look for common signs of the condition. The doctor may also ask about symptoms, such as swelling in your child’s hands and feet, a condition called dactylitis that may be a sign of inflammation or narrowing in the blood vessels.

The doctor may feel your child’s abdomen to see whether his or her spleen is enlarged. In addition, the doctor measures your child’s blood pressure to evaluate his or her risk of stroke.

Imaging Tests

Imaging tests are not used to diagnose sickle cell disease, but they play an important role in determining a child’s risk of stroke, lung problems, and bone and joint abnormalities caused by the condition.

Transcranial Doppler Ultrasound

A transcranial Doppler ultrasound may be used to see how blood flows through the arteries in the head and neck, which can determine your child’s risk of stroke. Our doctors recommend this ultrasound exam for children with sickle cell disease beginning when they are two years old.

The doctor places a special wand called a transducer on the back of the neck, above the cheekbone, in front of the ear, and over the eyelid. The transducer emits high-frequency sound waves that bounce off blood cells in the vessels, showing the doctor how fast the blood is flowing.

When blood vessels become narrowed, a child with sickle cell disease is at higher risk for stroke. He or she may therefore benefit from a blood transfusion, which reduces the child’s risk of stroke.

Children who have had a stroke or are at increased risk for one may be referred to a neuropsychologist at Hassenfeld Children's Hospital. This doctor can look for signs of learning disorders or developmental delays.

Chest X-rays

Chest X-rays use high-energy beams of light to take a snapshot of the lungs in children with sickle cell disease who have symptoms such as chest pain, shortness of breath, or cough. X-rays can be used to diagnose acute chest syndrome.

Abdominal Ultrasound

If your child has an enlarged or very painful abdomen, ultrasound may be used to look for other common complications, such as an enlarged spleen or gallstones.

In this test, the doctor places a wand called a transducer on your child’s abdomen. The transducer emits high-frequency sound waves that bounce off abdominal organs, creating a picture of the spleen and gallbladder.

Urine Test

Beginning when your child is 10 years old, our doctors may perform urine tests to measure the amount of protein in your child’s urine. People with kidney damage often have excess protein in their urine, because the kidneys’ filtering structures allow protein to leak out of the blood.

The doctor gives your child a sterile cup to urinate in. This urine sample may be tested in the office or sent to a laboratory for evaluation. If excess protein is found in the random sample, your child’s urine may be collected over a period of several hours to see whether there are any changes in the amount of protein eliminated at different times of the day.

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