Sickle Cell Trait

Know Your Sickle Cell Trait (SCT) Status. Get Screened for SCT.

Summary: Key Takeaways About Sickle Cell Trait

Sickle Cell Trait (SCT) is an inherited biological characteristic that can impact an individual’s reproductive and personal health considerations.
SCT evolved ages ago to protect against certain kinds of malaria. Because of this, SCT is most common among people with ancestry from regions with large populations of mosquitoes that transmit malaria; however, anyone can have SCT.
If one parent has SCT and the other parent has SCT or a similar red blood cell trait, they can have a child with sickle cell disease (SCD).
SCT is not a disease. Most people who have SCT do not notice any symptoms and live long, healthy lives.
There are rare cases in which SCT is connected to extreme medical issues, like renal medullary carcinoma (RMC) and sudden collapse following exercise.
Researchers have discovered that dehydration, exertion, and extreme changes in altitude can prompt medical complications associated with SCT.
People who have SCT should talk to their health care providers and family members about their trait status and discuss interventions to prevent and detect any potential medical issues.
If you do not know your SCT status, you should talk to your doctor about genetic screening.

Definition & Origin

Sickle cell trait (SCT), also known as Hemoglobin AS (HbAS), is a biological characteristic that occurs when an individual inherits one altered red blood cell gene, known as Hemoglobin S (HbS).
A gene is an inherited piece of biological information that is passed down from parents to children to determine the child’s individual characteristics.
It is theorized that SCT first evolved thousands of years ago to protect future generations of people from severe forms of malaria. Because of this, people living with SCT often live in, or have family roots from, regions with large populations of mosquitoes that transmit malaria.
Please note, people with SCT are not immune to malaria and may still fall ill to certain forms of the infectious disease, but it is usually less severe.

Genetics & Reproductive Health Considerations

Individuals born with SCT (HbAS) inherit one (1) of these red blood cell genes that evolved and altered over time, specifically Hemoglobin S (HbS), from one parent and one red blood cell gene that did not evolve or alter over time, specifically Hemoglobin A (HbA).
- Parent 1: HbA gene + Parent 2: HbS gene = Baby with SCT: HbAS

Meanwhile, individuals born with sickle cell disease (SCD) inherit two (2) Hemoglobin S genes (HbS) leading to Hemoglobin SS (HbSS), or one (1) hemoglobin S gene (HbS) and one (1) similar red blood cell gene.

Image Source: St. Jude Children’s Research Hospital Hematology Program

Image Source: St. Jude Children’s Research Hospital Hematology Program

When combined with the Hemoglobin S (HbS) gene, inheriting another similar red blood cell gene can lead to a person being born with SCD; common examples of these similar red blood cell genes include:
- Hemoglobin C (HbC)
- Hemoglobin D (HbD)
- Hemoglobin E (HbE)
- Hemoglobin O (HbO)
- Hemoglobin Beta (Hbβ)
Check out the table below for an overview of how these genes can be passed down and lead to pregnancy resulting in a baby with SCD:

Though not at risk of ever living with SCD themselves, individuals who have SCT, or a similar red blood cell trait, may have a child born with SCD with each pregnancy.
To learn more about different genetic traits related to sickle cell and inheriting SCD, check out this “Get Screened for Sickle Cell Trait” flyer and talk to a genetic counselor.

Risk Factors & Personal Health Considerations

SCT is not a disease. Most people who have SCT experience little to no related medical problems and live healthy, long lives.
While unusual, there are potential clinical complications associated with SCT that can arise in extreme circumstances.
Risk factors, such as dehydration, intense physical exertion, and high altitude, can make rare clinical complications associated with SCT more likely.
Potential clinical complications associated with SCT include:
Symptoms of these rare complications associated with SCT include blood in the urine and pain. Talk to your health care providers if you experience either of these symptoms.
It is important that people living with SCT take preventative interventions, like regularly drinking water and resting, when faced with these risk factors.
To learn more about how to detect and manage potential health complications, check out the Sickle Cell Trait Toolkit.

The Current State of SCT

Incidence:
- Roughly 3 million people live with SCT in the US (CDC)
- More than 100 million people live with SCT worldwide (ASH)
Most Affected Populations:
- SCT is most common among people whose ancestors come from malaria-endemic regions, like sub-Saharan Africa; warmer areas in the Western Hemisphere (South America, the Caribbean, and Central America); Saudi Arabia; India; and Mediterranean countries (Turkey, Greece, and Italy).
- However, anyone can have SCT.
Epidemiology:
- Growing and diversifying with globalization

Current Issues:
- Limited Knowledge of Individual SCT Status – minimal and inconsistent follow-up by health care providers on individual’s SCT status during medical visits and limited access to genetic counseling.
- Deployment of Improper SCT Testing Tools – common use of solubility tests, which can lead to inaccurate results by missing other inherited red blood cell genes related to sickle cell.
- Stigma and Confusion About SCT Throughout Society – misinformation and limited awareness about genetics and sickle cell throughout society.
- Faulty Pathology Reports Citing Causes of Death Due to SCT – rising trends of pathology reports that conflict with evidence and consensus-based guidance and reflect social and racial bias.
- Lack of SCT Research – need for more prospective studies on societal perspectives and clinical complications associated with SCT.

SCDC Stepping Forward: Our Progress

The SCD Coalition’s Sickle Cell Trait Task Force is working to address issues surrounding sickle cell trait by taking collective action.
To learn more about how the task force aims to take a stand, read its strategic goals listed below:

Educational Resources for Sickle Cell & Other Blood Disorders – Source: St. Jude Children’s Research Hospital Hematology Program
Family Planning Options for Couples with Sickle Cell Trait or Sickle Cell Disease – Source: Dr. Macy Early and Sickle Cell Reproductive Health Education Directive (SCRED)
Find a Genetic Counselor Directory – Source: National Society of Genetic Counselors (NSGC)
Know & Tell Sickle Cell Trait and Renal Medullary Carcinoma – Source: Sickle Cell Disease Association of America (SCDAA) and the Kidney Cancer Association
Operation Hydration – Source: As One Foundation
Position Statement on Sickle Cell Trait – Source: American Society of Hematology (ASH)
Sickle Cell Disease and Pregnancy – Source: March of Dimes
Sickle Cell Disease and Sickle Cell Trait Brochure – Source: SCDAA
Sickle Cell Trait – Source: Sick Cells
Sickle Cell Trait Awareness Campaign – California – Source: Cayenne Wellness Center
Sickle Cell Trait – Patient Education – Source: ASH
Sickle Cell Trait Toolkit – Source: Centers for Disease Control and Prevention (CDC), ASH, and SCDAA
Statement on Screening for Sickle Cell Trait and Athletic Participation – Source: ASH
What is Sickle Cell Trait? – Source: CDC
What is SCT – Source: Breaking the Sickle Cell Cycle (BTSSCC)

The status quo is unacceptable, and we are setting out to change it

People with sickle cell disease (SCD) are afflicted on two fronts — one by having a serious, chronic condition that inflicts pain and other complications — the other by a fragmented system of care.

Today, there are opportunities to transform this disease and the way we care for people with SCD. We are launching an international call to action on SCD by bringing together researchers, clinicians, individuals with sickle cell disease and their families, policymakers, and the private sector to focus our collective efforts and change the state of SCD around the world.

Get Involved

Our Members

The Sickle Cell Disease Coalition is composed of public health, research, and provider organizations, patient groups, faith-based organizations, federal agencies, industry representatives, and foundations with an interest in Sickle Cell Disease.

*Member belongs to the Steering Committee.

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The status quo is unacceptable & we are setting out to change it. Join us to #ConquerSCD! www.scdcoalition.org

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