Sickle cell trait is an inherited (genetic) condition that affects some of the hemoglobin in blood. Hemoglobin is a part of your red blood cells, which carry oxygen in your body. In sickle trait, some of the body’s normal hemoglobin is replaced with hemoglobin S, which is also called sickle hemoglobin.

Normal blood cells are round and shaped like doughnuts. Babies with sickle cell trait typically have enough normal hemoglobin to have normal shaped red blood cells, so they do not usually have any signs and symptoms.

However, when individuals with sickle cell trait experience certain extreme conditions (very high altitude, severe dehydration, or very extreme exercise), the sickle hemoglobin inside their cells may turn their blood cells sickle or crescent moon-shaped. When red blood cells become sickle shaped, they have a harder time bringing oxygen to the body, they break down more quickly, and can get stuck in the blood vessels.

1 in 13 African American babies are born with sickle cell trait in the United States.

People who inherit one sickle cell gene and one normal gene have sickle celltrait (SCT). People with SCT usually do not have any of the symptoms of sickle cell disease (SCD), but they can pass the trait on to their children.

How Sickle Cell Trait is Inherited

• If both parents have SCT, there is a 50% (or 1 in 2) chance that any child of theirs also will have SCT, if the child inherits the sickle cell gene from one of the parents. Such children will not have symptoms of SCD, but they can pass SCT on to their children.
• If both parents have SCT, there is a 25% (or 1 in 4) chance that any child of theirs will have SCD. There is the same 25% (or 1 in 4) chance that the child will not have SCD or SCT.

Diagnosis

SCT is diagnosed with a simple blood test. People at risk of having SCT can talk with a doctor or health clinic about getting this test.

Complications

Most people with SCT do not have any symptoms of SCD, although—in rare cases—people with SCT might experience complications of SCD, such as pain crises.
In their extreme form, and in rare cases, the following conditions could be harmful for people with SCT:

• Increased pressure in the atmosphere (which can be experienced, for example, while scuba diving).
• Low oxygen levels in the air (which can be experienced, for example, when mountain climbing, exercising extremely hard in military boot camp, or training for an athletic competition).
• Dehydration (for example, when one has too little water in the body).
• High altitudes (which can be experienced, for example, when flying, mountain climbing, or visiting a city at a high altitude).

More research is needed to find out why some people with SCT have complications and others do not.

SCT and Athletes

Some people with SCT have been shown to be more likely than those without SCT to experience heat stroke and muscle breakdown when doing intense exercise, such as competitive sports or military training under unfavorable temperatures( very high or low) or conditions.
Studies have shown that the chance of this problem can be reduced by avoiding dehydration and getting too hot during training.
People with SCT who participate in competitive or team sports (i.e. student athletes) should be careful when doing training or conditioning activities. To prevent illness it is important to:

• Set your own pace and build your intensity slowly.
• Rest often in between repetitive sets and drills.
• Drink plenty of water before, during and after training and conditioning activities.
• Keep the body temperature cool when exercising in hot and humid temperatures by misting the body with water or going to an air conditioned area during breaks or rest periods.
• Immediately seek medical care when feeling ill.

For people who don’t suspect they carry the sickle cell gene, having a baby with sickle cell disease can be heartbreaking. The illness is inherited and lasts a lifetime. Fifty years ago, half of children born with sickle cell disease died by age 10. Now they’re living into their 40s and 50s, thanks to therapies developed with NIH support. Researchers are now working on promising new treatments.

Sickle cell disease is a serious disorder in which the body makes red blood cells that have a sickle shape—like the letter C. These stiff, misshaped cells can lead to painful episodes, serious infections, organ damage and long-term anemia .

By some estimates, 70,000 to 100,000 Americans have sickle cell disease. Most are African Americans, although the disease also occurs in Hispanic Americans and others.

“It’s a rare disease in the U.S.,” says Dr. Gregory Kato, a sickle cell disease expert at NIH. “But sickle cell disease affects millions of people in Africa, as well as in Saudi Arabia, India, South America and other regions.”

The sickle cell gene has an even broader reach. More than 2 million Americans—including 1 in 12 African Americans—carry 1 copy of the abnormal gene. They’re said to have sickle cell trait. While they don’t have sickle cell disease, they can still pass the flawed gene to their children.

Sickle cell disease arises when you inherit 2 abnormal genes, 1 from each parent. The genes make a defective form of hemoglobin, the oxygen-carrying protein in red blood cells. Affected cells collapse into a sickle shape. The sickled cells bunch together and reduce blood flow through your blood vessels. That can cause severe and sudden pain throughout the body and lead to stroke or organ damage from lack of oxygen. This medical emergency, called a sickle cell crisis, can be treated with pain medication and blood transfusions.

A blood test can show if you have sickle cell disease or the trait. All states now test newborns as part of their screening programs, so treatment can begin early.

Severe sickle cell disease can be treated with a medicine called hydroxyurea. It helps to prevent red blood cells from sickling. Hydroxyurea doesn’t cure sickle cell disease, but it can make it milder. And it was recently shown to be safe and effective for very young children.

“Although the treatment of sickle cell disease pain crisis hasn’t changed much since the discovery of the disease a hundred years ago, there are more new treatments now under investigation than in any time in history,” says Kato. “All clinical drug trials are always speculative. Most don’t work out, but some do. Biomedical scientists like us are working towards the future.”

If you have sickle cell disease, take steps to prevent and control its complications by maintaining a healthy lifestyle. If you’re at high risk of having a child with sickle cell anemia and are planning to have children, ask your health care professional about genetic counseling.

Living with Sickle Cell Disease

• See a sickle cell disease expert regularly.
• Visit your eye doctor to check for eye damage.
• Work with your doctor to find ways to manage pain.
• Make sure babies and young children get needed antibiotics and routine vaccinations to prevent infections.
• Seek specialized prenatal care if you have sickle cell disease and are pregnant or planning to become pregnant.
• Join a patient support group.

Sickle cell trait is caused by a change in the HBB gene. This gene gives the body instructions for making beta-globin, a protein found in hemoglobin.

The change in HBB creates an abnormal beta-globin called hemoglobin S (HbS). Under extreme conditions, the abnormal beta-globins may cause red blood cells to be sickle-shaped instead of round.

Normal Function

The HBB gene provides instructions for making a protein called beta-globin. Beta-globin is a component (subunit) of a larger protein called hemoglobin, which is located inside red blood cells. In adults, hemoglobin consists of four protein subunits: usually two subunits of beta-globin and two subunits of a protein called alpha-globin, which is produced from another gene called HBA. Each of these protein subunits is attached (bound) to an iron-containing molecule called heme; the iron in the center of each heme can bind to one oxygen molecule. Hemoglobin within red blood cells binds to oxygen molecules in the lungs. These cells then travel through the bloodstream and deliver oxygen to tissues throughout the body.

Health Conditions Related to Genetic Changes

Beta thalassemia

Hundreds of variants (also known as mutations) in the HBB gene have been found to cause beta thalassemia. Most of the variants involve a change in a single DNA building block (nucleotide) within or near the HBB gene. Other variants insert or delete a small number of nucleotides in the HBB gene.

HBB gene variants that decrease beta-globin production result in a condition called beta-plus (β+) thalassemia. Variants that prevent cells from producing any beta-globin result in beta-zero (β0) thalassemia.

Problems with the subunits that make up hemoglobin, including low levels of beta-globin, reduce or eliminate the production of this molecule. A lack of hemoglobin disrupts the normal development of red blood cells. A shortage of mature red blood cells can reduce the amount of oxygen that is delivered to tissues to below what is needed to satisfy the body's energy needs. A lack of oxygen in the body's tissues can lead to poor growth, organ damage, and other health problems associated with beta thalassemia.

Methemoglobinemia, beta-globin type

Variants in the HBB gene have been found to cause methemoglobinemia, beta-globin type, which is a condition that alters the hemoglobin within red blood cells. These variants often affect the region of the protein that binds to heme. For hemoglobin to bind to oxygen, the iron within the heme molecule needs to be in a form called ferrous iron (Fe2+). The iron within the heme can change to another form of iron called ferric iron (Fe3+), which cannot bind to oxygen. Hemoglobin that contains ferric iron is known as methemoglobin and is unable to efficiently deliver oxygen to the body's tissues.

In methemoglobinemia, beta-globin type, variants in the HBB gene alter the beta-globin protein and promote the heme iron to change from ferrous to ferric. This altered hemoglobin gives the blood a brown color and causes a bluish appearance of the skin, lips, and nails (cyanosis). The signs and symptoms of methemoglobinemia, beta-globin type are generally limited to cyanosis, which does not cause any health problems. However, in rare cases, severe methemoglobinemia, beta-globin type can cause headaches, weakness, and fatigue.

Sickle cell disease

Sickle cell anemia (also called homozygous sickle cell disease or HbSS disease) is the most common form of sickle cell disease. This form is caused by a particular variant in the HBB gene that results in the production of an abnormal version of beta-globin called hemoglobin S or HbS. In this condition, hemoglobin S replaces both beta-globin subunits in hemoglobin.

The variant that causes hemoglobin S changes a single protein building block (amino acid) in beta-globin. Specifically, the amino acid glutamic acid is replaced with the amino acid valine at position 6 in beta-globin, written as Glu6Val or E6V. Replacing glutamic acid with valine causes the abnormal hemoglobin S subunits to stick together and form long, rigid molecules that bend red blood cells into a sickle (crescent) shape. The sickle-shaped cells die too early, which can lead to a shortage of red blood cells (anemia). The sickle-shaped cells are rigid and can block small blood vessels, causing severe pain and organ damage.

Variants in the HBB gene can also cause other abnormalities in beta-globin, leading to other types of sickle cell disease. These abnormal forms of beta-globin are often designated by letters of the alphabet or sometimes by a name. In these other types of sickle cell disease, just one beta-globin subunit is replaced with hemoglobin S. The other beta-globin subunit is replaced with a different abnormal variant, such as hemoglobin C or hemoglobin E.

In hemoglobin SC (HbSC) disease, the beta-globin subunits are replaced by hemoglobin S and hemoglobin C. Hemoglobin C results when the amino acid lysine replaces the amino acid glutamic acid at position 6 in beta-globin (written Glu6Lys or E6K). The severity of hemoglobin SC disease is variable, but it can be as severe as sickle cell anemia. Hemoglobin E (HbE) is caused when the amino acid glutamic acid is replaced with the amino acid lysine at position 26 in beta-globin (written Glu26Lys or E26K). In some cases, the hemoglobin E variant is present with hemoglobin S. In these cases, a person may have more severe signs and symptoms associated with sickle cell anemia, such as episodes of pain, anemia, and abnormal spleen function.

Other conditions, known as hemoglobin sickle-beta thalassemias (HbSBetaThal), are caused when variants that result in hemoglobin S and beta thalassemia (described above) occur together. Variants that combine sickle cell disease with beta-zero (β0) thalassemia lead to severe disease, while sickle cell disease combined with beta-plus (β+) thalassemia is generally milder.

Other disorders

Hundreds of variations have been identified in the HBB gene. These changes result in the production of different versions of beta-globin. Some of these variations cause no noticeable signs or symptoms and are found when blood work is done for other reasons, while other HBB gene variations may affect a person's health. Two of the most common variants are hemoglobin C and hemoglobin E (described above).

Hemoglobin C (HbC), caused by the Glu6Lys variant in beta-globin, is more common in people of West African descent than in other populations. People who have two hemoglobin C subunits in their hemoglobin, instead of normal beta-globin, have a mild condition called hemoglobin C disease. This condition often causes chronic anemia, in which the red blood cells are broken down prematurely.

Hemoglobin E (HbE), caused by the Glu26Lys variant in beta-globin, is a variant of hemoglobin most commonly found in the Southeast Asian population. When a person has two hemoglobin E subunits in their hemoglobin in place of beta-globin, a mild anemia called hemoglobin E disease can occur. In some cases, the variants that produce hemoglobin E and beta thalassemia (described above) are found together. People with this hemoglobin combination can have signs and symptoms ranging from mild anemia to severe thalassemia major.

Other Names for This Gene

• beta globin
• beta-globin
• HBB_HUMAN
• hemoglobin beta gene
• hemoglobin, beta
• hemoglobin--beta locus

Genomic Location

Sickle cell trait is a genetic condition. Babies inherit it from their biological (birth) parents.

• Babies inherit sickle cell trait when one parent passes down a nonworking HBB gene to their baby.
  • People with one normal copy and one hemoglobin S copy of the HBB gene are said to have sickle cell trait (sometimes also called being a carrier).
  • People with sickle cell trait may pass down a hemoglobin S copy of the gene to their children.
  • If two parents both have sickle cell trait, each have a hemoglobin S copy of the HBB gene. They have a 1 in 2 chance of having a child with sickle cell trait and they have a 1 in 4 chance of having a child with S,S disease.
  • People with sickle cell trait often do not know they are carriers of a hemoglobin S copy of the HBB gene before having a child with sickle cell trait or S,S disease.
  • Parents who already have a child with sickle cell trait still have a 1 in 2 chance of having another child with sickle cell trait. This 1 in 2 chance stays the same for all future children.
• Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it.

Most individuals with sickle cell trait will never have any signs and symptoms of the condition. Rarely, signs of sickle cell trait may appear when a baby or individual is under certain conditions. Conditions that can lead to signs and symptoms of sickle cell trait are:

• Low oxygen levels (like after extreme exercise or training)
• Dehydration (too little water in the body)
• High altitudes (flying or visiting a city located high above sea level)

Signs of the condition may include the following:

• Pain or painful swelling in hands or feet
• Difficulty breathing

Sometimes people with SCT experience blood in the urine, a condition called hematuria. This can be a sign of a serious medical condition, so it requires a thorough medical evaluation. Learn more about how you can protect yourself.

People with sickle cell trait (SCT) are generally healthy and rarely have problems with their spleens. However, some people with SCT experience a serious condition called splenic infarct, the death of tissue in the spleen. Learn more about SCT and damage to the spleen, a rare complication of SCT.

People with sickle cell trait (SCT) who experience an eye injury are more likely to develop eye problems including bleeding in the eye followed by a buildup of pressure inside the eye. This can lead to blurry vision or loss of vision, and may even cause permanent eye damage. Therefore, if you have SCT and have suffered an eye injury, it is important that you get checked out right away by an eye specialist who can closely monitor your care.

My doctor said I’m at risk for glaucoma post-hyphema? What’s that?

Hyphema is the presence of blood in the fluid-filled space inside the eye between the clear covering of the eye (the cornea) and the colored part of the eye (the iris). This space between the cornea and iris is called the anterior chamber of the eye.

This bleeding, or hyphema, into the anterior chamber may follow an eye injury. Hyphema is rare, but it is serious.

Glaucoma, or increased pressure within the eye, can occur after hyphema. It is called glaucoma post-hyphema.

If you have SCT and have experienced an eye injury, you are more likely to develop eye problems such as glaucoma posthyphema. Therefore, after an eye injury, you will need to be monitored closely by an eye specialist, called an ophthalmologist.

How can I tell if I have glaucoma post-hyphema? What are the warning signs?

Hyphema occurs after trauma or injury to the eye. The symptoms of hyphema include pain, discomfort and difficulty seeing in bright light, and vision changes, such as blurred or decreased vision, or total loss of vision. Following hyphema, if the vision problems do not go away with treatment, it may be due to either a buildup of pressure inside the eye (glaucoma) or more bleeding.

I have SCT. What should I do if I think I may have glaucoma post-hyphema

If you experience eye trauma or injury, you should seek immediate medical attention in an emergency department and let the treating healthcare provider know that you have SCT and have experienced eye trauma.

If I have SCT and I develop bleeding in my eye, is there anything I can do to prevent further damage?

Yes! People who experience bleeding in the eye can help prevent further damage by

• Limiting their physical activity;
• Avoiding situations that could lead to further eye trauma;
• Wearing eye protection on their injured eye (an eye patch with a shield); and
• Getting prompt medical care from an ophthalmologist

The hemoglobin A1C (A1C) test can be unreliable for diagnosing or monitoring diabetes and prediabetes in people with inherited hemoglobin variants, also called hemoglobinopathies. Hemoglobins S and E are prevalent variants in people of African, Mediterranean, or Southeast Asian descent. These variants interfere with some A1C tests—both laboratory and point-of-care tests. If A1C tests are at odds with blood glucose testing results, interference should be considered. Reliable A1C tests that do not cause interference with hemoglobin variants are available. More information about appropriate assay methods to use for hemoglobin variants is available from the NGSP at www.ngsp.org. Also, alternative tests may be needed for people with any disorder that affects red blood cells or hemoglobin.

When to Suspect that a Patient with Diabetes Has a Hemoglobinopathy

Most people who are heterozygous—having one variant gene and one standard hemoglobin gene—for a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin. Health care providers should suspect the presence of a hemoglobinopathy when

• an A1C result is different than expected
• an A1C result is above 15 percent
• results of self-monitoring of blood glucose have a low correlation with A1C results
• a patient’s A1C result is radically different from a previous A1C result following a change in laboratory A1C methods

Statistically Speaking

Hemoglobins S and C

African Americans have an increased risk of inheriting sickle cell trait, the condition in which people have both hemoglobin A (HbA), the usual form of hemoglobin, and hemoglobin S (HbS), a variant. African Americans are also at risk for having hemoglobin C (HbC), another variant. About one in 12 African Americans has sickle cell trait. About 12.7 percent of African Americans ages 18 years or older have diabetes. Therefore, many African Americans have both diabetes and sickle cell trait.

Hemoglobin E

People of Southeast Asian descent are at risk for having hemoglobin E (HbE), another hemoglobin variant. Prevalence of diabetes in Asian Americans varies among subpopulations. About 8 percent of Asian Americans ages 18 years or older have diabetes.

Hemoglobinopathies

Hemoglobin is composed of heme—the portion of the molecule containing iron—and globin—a protein made up of amino acid chains. Hemoglobin variants occur when mutations in the globin genes result in changes in the amino acids of the globin protein. Hundreds of variants have been identified; a small number of variants are common and have clinical significance. Variants significant to A1C testing are listed in Table 1.

These variants are inherited in an autosomal recessive manner, affecting people in the following ways. People who are

• homozygous, with a condition such as hemoglobin SS (HbSS), have a copy of the variant gene from each parent and generally have sickle cell disease.
• heterozygous, with a condition such as hemoglobin S (HbS), have a copy of the variant gene from one parent and are said to have a trait or to be carriers and are usually asymptomatic.
• compound heterozygous, with a condition such as hemoglobin SC (HbSC), have inherited genes for two variants––HbS from one parent and HbC from the other. These patients may have less severe sickle cell symptoms.

Detecting Hemoglobinopathies

If a health care provider suspects that a patient may have a hemoglobinopathy, carrier status can be detected using hemoglobin electrophoresis, high-performance liquid chromatography (HPLC), or isoelectric focusing.

Alternatively, a health care provider can use an assay that does not have interference with any variant. More information is provided in the NIDDK health topic, Information about Assay Methods for Patients with Hemoglobinopathies.

Technically speaking...

The A1C test measures the amount of glycated hemoglobin in the blood, which reflects average blood glucose levels over the preceding 3 months. Also called the hemoglobin A1C, HbA1c, or glycohemoglobin test, the A1C test is based on the addition of glucose to hemoglobin over the typical 120-day life span of a red blood cell.

Formation of glycated proteins is proportional to the concentration of glucose in the blood. However, the A1C test is a weighted average, with the glucose level of the preceding 30 days contributing more to the test result than glucose levels 90 to 120 days earlier. Thus, clinically significant changes in glucose can be seen in the A1C without waiting 120 days for red blood cell turnover.

When the A1C test is used for diagnosis, the blood sample must be sent to a laboratory that uses an NGSP-certified method for analysis to ensure the results are standardized.

More information for health care providers about the A1C test is provided in the NIDDK health topics:

• The A1C Test and Diabetes
• Comparing Tests for Diabetes and Prediabetes: A Quick Reference Guide

Effect of Hemoglobinopathies on A1C Test Results

Laboratories use many different assay methods for measuring A1C, but some of these methods can give inaccurate results when the patient has a hemoglobin variant such as sickle cell trait or if there is an elevated level of HbF. Health care providers or patients interested in getting information about the accuracy of a particular A1C method for patients with hemoglobin variants should first find out which method their laboratory is using.

With some assay methods, A1C tests in patients with hemoglobinopathies result in falsely high outcomes, overestimating actual average blood glucose levels for the previous 3 months. Health care providers may then falsely diagnose patients or prescribe more aggressive treatments, resulting in increased episodes of hypoglycemia. Some methods used with certain hemoglobinopathies may result in falsely low outcomes, leading to undertreatment of diabetes.

Health care providers should not use the A1C test for patients with a disease condition such as HbSS, HbCC, or HbSC. Even if an assay does not interfere with their variant, these patients may suffer anemia, increased red blood cell turnover, and transfusion requirements, which can adversely affect A1C as a marker of long-term glycemic control.

See “Other Conditions That Can Affect A1C Test Results” for information about other conditions that may give false test results. Health care providers should consider alternative forms of testing for these patients, such as glycated serum protein or glycated albumin.

Common Types of Hemoglobinopathies

The following table summarizes the affected populations, prevalence, and outcomes of common hemoglobinopathies. These hemoglobinopathies may either falsely raise or lower A1C results, depending on the variant and the assay method.

Table 1. Common hemoglobinopathies: populations affected, prevalence, and outcomes

Information about Assay Methods for Patients with Hemoglobinopathies

The NGSP provides a table on its website at www.ngsp.org describing the effects of frequently encountered Hb variants and derivatives on glycohemoglobin measurement for more than 20 assay methods. The NGSP website also includes a list of references for the information summarized in the table.

The NGSP has worked with manufacturers and developed a network of reference laboratories to ensure the availability of assay methods without clinically significant HbAS or HbAC interference. In 2011, per the NGSP website, only about 4.2 percent of laboratories were using methods resulting in significant HbAS or HbAC interference. See www.ngsp.org for updates.

Alternative Tests

Health care providers may wish to consider using other measures of average blood glucose levels, such as the fructosamine test, also called glycated serum protein or glycated albumin, with patients who have hemoglobinopathies where an accurate A1C result cannot be obtained. However the fructosamine test shows average glucose levels over a much shorter period of time than the A1C test, usually about 2 to 3 weeks. Also, the fructosamine test is not standardized and the relationship of results of this test to glucose levels or risk for complications has not been established.

Other Conditions That Can Affect A1C Test Results

False A1C results may also occur in people with other problems that affect their blood or hemoglobin, regardless of which assay is used. For example, a falsely low A1C result can occur in people with

• anemia
• heavy bleeding

A falsely elevated A1C result can occur in people who

• are very low in iron, for example, those with iron deficiency anemia

Other causes of false A1C results include

• kidney failure
• liver disease

More information is available for patients with diabetes about hemoglobin variants and the A1C test in the NIDDK health topic, For People of African, Mediterranean, or Southeast Asian Heritage: Important Information about Diabetes Blood Tests.

Points to Remember

• The hemoglobin A1C (A1C) test can be unreliable for diagnosing or monitoring diabetes and prediabetes in people with inherited hemoglobin variants, also called hemoglobinopathies.
• Hemoglobins S and E are prevalent variants in people of African, Mediterranean, or Southeast Asian descent. These variants interfere with some A1C tests—both laboratory and point-of-care tests.
• With some assay methods, A1C tests in patients with hemoglobinopathies result in falsely high outcomes, overestimating actual average blood glucose levels for the previous 3 months. Health care providers may then falsely diagnose patients or prescribe more aggressive treatments, resulting in increased episodes of hypoglycemia.
• Some methods used with certain hemoglobinopathies may result in falsely low outcomes, leading to undertreatment of diabetes.
• Most people who are heterozygous—having one variant gene and one standard hemoglobin gene—for a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin.
• Health care providers should suspect the presence of a hemoglobinopathy when
  • an A1C result is different than expected
  • an A1C result is above 15 percent
  • results of self-monitoring of blood glucose have a low correlation with A1C results
  • a patient’s A1C result is radically different from a previous A1C result following a change in laboratory A1C methods
• Health care providers or patients interested in getting information about the accuracy of a particular A1C method for patients with hemoglobin variants should first find out which method their laboratory is using.
• Reliable A1C tests that do not cause interference with hemoglobin variants are available.
• When the A1C test is used for diagnosis, the blood sample must be sent to a laboratory that uses an NGSP-certified method for analysis to ensure the results are standardized.
• Health care providers should not use the A1C test for patients with a disease condition such as HbSS, HbCC, or HbSC. Even if an assay does not interfere with their variant, these patients may suffer anemia, increased red blood cell turnover, and transfusion requirements, which can adversely affect A1C as a marker of long-term glycemic control.
• Alternative tests may be needed for people with any disorder that affects red blood cells or hemoglobin.

Sickle cell trait is found in the same newborn screening test done testing for S,S disease. This screening requires collecting a small amount of blood from your baby’s heel. Screening measures certain types of hemoglobins in your baby’s blood. Babies with different types of hemoglobins (specifically hemoglobin S) might have sickle cell trait.

What Happens After an Out-of-Range Screening Result?

If your baby’s blood spot screening result shows that your baby might have sickle cell trait, your baby’s health care provider should let you know before or at your baby’s first well child visit. Together, you will discuss the results.

An out-of-range screening result suggesting sickle cell trait usually means that your baby does have sickle cell trait, but your baby will need more follow-up testing to know for sure.

Your baby may need the following tests after a sickle cell trait screening result:

• Blood tests
• Genetic testing using a blood sample

False-positive newborn screening results for this condition are rare. However, screening samples that are collected after a baby receives red blood cells from someone else (a red cell transfusion) will be inaccurate.

Newborn screening helps babies lead healthier lives. If your baby has a sickle cell trait screening result, follow up with your baby’s health care provider.

Most individuals with sickle cell trait will never need treatment. Treatment is only usually needed if an individual starts to have signs or symptoms.

Community-based organizations (CBOs) are local agencies that provide services, education, and support to families affected by sickle cell conditions like sickle cell trait.

What is sickle cell trait?

Sickle cell trait occurs when a person carries a single copy of the sickle globin gene inherited from one parent along with a normal globin gene from the other parent. The globin genes direct red blood cells in the bone marrow to produce hemoglobin, a protein that carries oxygen in red blood cells throughout the body. In most cases, people living with sickle cell trait experience no symptoms and lead normal lives. Because some persons with sickle cell trait have complications from the condition, research is needed to better understand when and how sickle cell trait might affect a person’s health. About 2.5 million people in the United States live with sickle cell trait. Sickle cell trait is different from sickle cell disease, also known as sickle cell anemia.

What is the difference between sickle cell trait and sickle cell disease?

People with sickle cell trait carry only one copy of the altered hemoglobin gene and rarely have any clinical symptoms related to the disease. In contrast, people with sickle cell disease carry two copies of the altered hemoglobin gene. With two copies of the altered gene, the red blood cells are destroyed rapidly and patients have chronic, severe anemia, or low hemoglobin levels. Red blood cells become misshapen, many of which take the “C” or sickle shape that gives the disease its name. Without proper treatment, a person with sickle cell disease can develop recurrent episodes of pain and may have life-threatening complications, including damage to organs such as brain, bones, lungs, kidneys, liver and heart. The disease affects between 70,000 and 100,000 Americans and is most common in people of African, Middle Eastern, Mediterranean, Central and South American and Asian Indian origin or descent.

What does it mean if someone has sickle cell trait?

Most people who have sickle cell trait will never experience any medical complications. However, in rare instances, some people who have sickle cell trait can experience medical complications when performing intense physical activity. Several of the risks to persons with sickle cell trait occur when they engage in high intensity physical activity or are active at higher elevations such as mountains or unpressurized airplanes. Persons with sickle cell trait occasionally experience damage to their kidneys from sickling in sections of the kidney. People with sickle cell trait should be aware of their condition for family planning purposes because they can pass the gene onto their children. If both parents have sickle cell trait, there is a greater chance that one or more of their children will be born with sickle cell disease.