Screening for Sickle Cell Trait

Reviewed by: HU Medical Review Board | Last reviewed: February 2023

People who have 1 gene for sickle hemoglobin and 1 gene for normal hemoglobin have sickle cell trait (SCT). They usually do not show symptoms of sickle cell disease, but they are carriers and can pass the sickle hemoglobin gene to their children.

The rate of sickle cell trait varies with ethnicity, but it is present in every racial population. Most people are diagnosed at birth during routine newborn screening. Upon diagnosis with SCT, the family can get education and counseling concerning health and decisions about reproduction.

How common is sickle cell trait?

About 1.5 percent of babies born in the United States have sickle cell trait. In other words, about 1 out of every 65 babies is diagnosed with SCT.1,2

The rate of SCT varies for different races and ethnicities, but people of every racial/ethnic population have SCT. For example, SCT is diagnosed in about:1,2

  • 1 out of 13 Black newborns
  • 1 out of 150 Hispanic newborns
  • 1 out of 330 white newborns
  • 1 out of 450 Asian or Pacific-Islander newborns

How do I know if my child or I have it?

Doctors diagnose sickle cell disease or sickle cell trait using blood tests that identify abnormal hemoglobin types. All babies in the United States are now screened with a simple blood test when they are born. The purpose of universal newborn diagnostic testing is to begin routine care before symptoms begin. Diagnostic testing may also happen during pregnancy (prenatal testing) or later in life (during adolescence and adulthood).3,4

Newborn screening

Newborn screening is the most common way that people are diagnosed with sickle cell disease or sickle cell trait. The test uses blood from a heel prick to identify abnormal types of hemoglobin proteins.5

Newborns with sickle cell anemia (HbSS) have mostly fetal hemoglobin (HbF) with a small amount of sickle hemoglobin (HbS). They have no normal hemoglobin (HbA). This is called an FS pattern. Newborns with other types of sickle cell disease may also show an FS pattern.3,6

Doctors then determine the specific type of sickle cell disease by testing family members, testing the baby’s DNA, or repeating the hemoglobin test in a couple of months. Upon diagnosis, doctors will begin providing education to the family and routine care to the child.3,6

Newborns with sickle cell trait will have HbF, HbA, and HbS. This is called an FAS pattern. Within a few months, HbF levels will decrease and the child will have HbA and HbS. This is then called HbAS. Upon diagnosis, the family can receive education about:3,6

  • The genetic inheritance of sickle cell trait
  • Any limitations that need to be placed on the child’s activities
  • How their own sickle cell status could affect their future children

Prenatal testing

Prenatal testing is a safe but invasive procedure offered during early pregnancy to couples whose children are at risk of having sickle cell disease. The test uses a DNA sample from the developing baby at 8 to 10 weeks of gestation. The decision to have this test is complicated and personal and should be determined by the mother with informational support from doctors and genetic counselors.3,7

Testing in older children and adults

Many people with sickle cell trait may be undiagnosed or unaware of their diagnosis. This is the case for many young people who immigrate from a country where they were not screened. It is also common for people with sickle cell trait to forget their diagnosis because they never showed symptoms.6,8

You may then be diagnosed with sickle cell trait as an adult when a family member is diagnosed with sickle cell trait or sickle cell disease. Doctors will then give you access to educational material and genetic counseling services.3

How do I know if my future child is at risk of having sickle cell disease?

If you have sickle cell trait, your child may inherit the sickle hemoglobin gene and have sickle cell trait. If you and your partner both have sickle cell trait, your child may inherit 2 genes for sickle hemoglobin and have sickle cell disease.9

You can get more information specific to your situation from a genetic counselor. With a genetic counselor, you can discuss:3,6

  • How sickle cell trait and sickle cell disease are acquired
  • The exact risk of your child having sickle cell trait or sickle cell disease based on your and your partner’s sickle cell status
  • Health problems that can occur in sickle cell disease
  • Family planning options
  • Reasons that you may decide to have or not have children

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