American Society of Hematology

Frequently Asked Questions Regarding Sickle Cell Trait

Published on: January 25, 2012

Sickle cell trait is an inherited blood disorder affects approximately 8 percent of African-Ameriacns. Unlike sickle cell disease, a serious illness in which patients have two genes that cause the production of abnormal hemoglobin, individuals with sickle cell trait carry only one defective gene and typically live normal lives. Rarely, extreme conditions such as severe dehydration and high-intensity physical activity can lead to serious health issues, including sudden death, in these individuals.

Frequently Asked Questions of Interest to Medical Experts

Q: What is sickle cell trait?

A: Sickle cell trait means that someone is a carrier for one copy of the gene that causes sickle cell disease. Red blood cells contain some abnormal sickle hemoglobin, but most of the hemoglobin in each red blood cell is normal.

Q: Who is affected by sickle cell trait?
A:
Millions of Americans and hundreds of millions of individuals worldwide have sickle cell trait. Most people with sickle cell trait are of African ancestry, but not exclusively.  

Q: How does someone get sickle cell trait?
A: Sickle cell is an inherited condition. It cannot be acquired in any other way. 

Q: How does an individual know if he or she has sickle cell trait? How is it diagnosed?
A: Sickle cell trait can only be detected by a blood test. Sickle cell testing should be performed by a knowledgeable provider, who can interpret test results and give comprehensive counseling.

Q: What is the difference between sickle cell trait and sickle cell disease?
A: Sickle cell trait is due to inheritance of one copy of the sickle gene. Sickle cell disease results from the inheritance of two abnormal genes, one from each parent. Sickle cell trait is not a mild form of sickle cell disease. 

Q: What health complications are associated with sickle cell trait?
A: Most people with sickle cell trait have no symptoms and will not have any health complications. Occasionally people with sickle cell trait can have painless hematuria. Under extreme conditions such as high altitude, severe dehydration, or very high intensity physical activity typically associated with high temperatures, red cells can become deformed or sickled. Complications include muscle breakdown (rhabdomyolysis), reduced blood supply to the spleen (ischemia/infarction), or increased pressure in the eye (glaucoma) following eye injuries. Finally, a very rare form of kidney cancer (renal medullary carcinoma) has been associated with sickle cell trait.

Q: Can an individual with sickle cell trait participate in athletics/exercise?
A:
Sickle cell trait should not be an impediment for participation in athletics or physical exercise. Maintaining good hydration and understanding how to avoid injuries can make exercise safer for ALL individuals, including those with sickle cell trait.

Q: What precautions should an individual with sickle cell trait take when participating in sports or exercise? How can an individual with sickle cell trait prevent exercise-related complications?
A:
Individuals with sickle cell trait should consider the same precautions that can prevent injuries and exercise-related illnesses as people who do not have sickle cell trait. These include being mindful of heat and humidity, drinking adequate fluids, taking rest breaks as needed, and not exceeding their current level of fitness.

Q: When should an individual with sickle cell trait see a medical professional?
A:
Individuals should see a doctor when they have blood in their urine, experience eye trauma, or have  heat exhaustion or a similar event.

Q: When should an individual with sickle cell trait see a counselor?
A:
Many individuals with sickle cell trait are unaware of their status. Hematologists recommend that all individuals at risk for sickle cell trait be aware of their trait status and be evaluated by primary-care providers and/or specialists, such as hematologists or genetic counselors.

Q: What symptoms will people with sickle cell trait experience that will let them know that they have taken their training too far? 
A:
The same symptoms that would allow you to identify any athlete that has trained too far.

Q: What precautions should coaches make when they have an athlete with sickle cell trait on their team?
A:
The same steps that the coach would take for any athlete at risk for heat exhaustion.

Frequently Asked Questions of Interest to Patients/Consumers

Q: What is sickle cell disease?
A:
Sickle cell disease is the most common inherited blood disorder in the U.S. It results from the inheritance from both parents of two defective or abnormal genes for hemoglobin, the substance in red blood cells that helps carry oxygen. The abnormal hemoglobin in sickle cell disease causes the cells to change shape under certain conditions, which can cause anemia, severe pain, strokes, other disabilities, and in some cases premature death.

Q: What is sickle cell trait?
A:
Sickle cell trait means that someone carries or has inherited a single copy of the gene that causes sickle cell disease. It is not a disease. In general, people with sickle cell trait enjoy normal life spans with no medical problems related to sickle cell trait.

Q: How common is sickle cell trait?
A:
There are 1 million to 3 million Americans with sickle cell trait. It is estimated that 8 to 10 percent of African Americans have sickle cell trait. Sickle cell trait can also affect Hispanics, South Asians, Caucasians from southern Europe, and people from Middle Eastern countries. More than 100 million people worldwide have sickle cell trait.

Q: Can sickle cell trait ever evolve or convert to sickle cell disease?
A:
No. Sickle cell trait can never become sickle cell disease. It is possible for an individual with sickle cell trait to pass the gene to their children.

Q: Are there any complications of sickle cell trait? If so, what are they, and how commonly do complications occur?
A:
Most people with sickle cell trait have no symptoms and will not have any health complications.  Occasionally people with sickle cell trait can have blood in their urine. Under extreme conditions such as high altitude, severe dehydration or very high intensity physical activity, red cells can become deformed or sickled. Complications include muscle breakdown (rhabdomyolysis), reduced blood supply to the spleen (ischemia/infarction), or increased pressure in the eye (glaucoma) following eye injuries. Finally, a very rare form of kidney cancer (renal medullary carcinoma) has been associated with sickle cell trait.

Q: What, if any, precautions should someone with sickle cell trait take for participation in sports?
A:
Universal precautions undertaken by all participants will make sports safer by reducing the risk of injuries and over-exertion. These precautions include drinking adequate amounts of fluid and taking rest breaks as needed, especially if the activity is new or if the temperature and humidity are high.  If it is an organized sports activity, there should be staff present who can recognize when a participant needs medical attention.

Q: Is screening dangerous? Can someone be harmed by having a screening test performed?
A: The actual test for screening is a blood test, which is not dangerous. Prior to having any genetic test, it is very important to have accurate information about what the results may mean. Once your results are available, the discussion for the interpretation of the results must be with a professional who has knowledge and experience with sickle cell. Inaccurate or incomplete counseling may be harmful if you make decisions based on erroneous information.  Screening tests can also be harmful if your rights to privacy are not protected because of discrimination that may occur by others.

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