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What is Sickle Cell Trait?
Sickle cell trait is a descriptive term for a hereditary condition in which the individual has one normal gene for hemoglobin and one abnormal gene for hemoglobin.1 Hemoglobin is a protein in the red blood cells in your body responsible for oxygen transport. Approximately 99% of the oxygen transported in blood is bound to hemoglobin inside the red blood cells.2
Sickle cell trait is generally a benign condition that does not develop or change over time. In general, it is a condition that does not affect the life span of the individual. As individuals with sickle cell trait get older, they may become unable to concentrate urine normally. This is not usually an issue for high school or college age athletes.1
Sickle cell trait is not a barrier to exercise or participation in sport.3
What is Sickle Cell Anemia?
Sickle cell anemia is the hereditary condition in which the individual has two abnormal hemoglobin genes.1 Sickle cell anemia is a lifelong disease that can cause painful episodes sometimes requiring hospitalization. Sickle cell trait will not develop into sickle cell anemia at any time. Carriers of sickle cell trait usually do not have any of the clinical symptoms of sickle cell anemia however; they may pass this onto their children.4
How do I find out if I or my child has sickle cell trait?
Sickle cell status is tested at birth and the results may be able to be found in state newborn screening records and/or with your primary care provider.
If you have never had sickle cell testing for your child, a simple blood test will yield results. NCAA athletes should contact their sports medicine department for any questions regarding sickle cell trait screening.
What are some of the complications of sickle cell trait for the physically active?
Although sickle cell trait will not turn into the disease, it is possible to have clinical symptoms when exercising under extreme conditions of physical exertion and/or low oxygen levels.1
Athletes with sickle cell trait are potentially more vulnerable to gross hematuria, splenic infarction, exertional heat stroke, severe muscle breakdown (rhabdomyolysis) and potentially even sudden death when participating in strenuous exercise under intense environmental conditions.1,3,5
Gross Hematuria: Gross hematuria is defined as visible blood in the urine. Usually from the left kidney, gross hematuria is an occasional complication of sickle cell trait. Any athlete experiencing this should consult a physician for return to play protocol.1
Exertional Sickling. Exertional sickling is a potentially life-threatening condition resulting from the sickling of red blood cells during intense exercise. Sickling results in muscular ischemia and collapse, whereby the athlete may experience intense muscular pain, rhabdomyolysis, and other serious metabolic problems.2 The athlete initially will still be conscious and able to talk and may complain of muscular pain, however this is not to be confused with muscle cramping. Exertional sickling is a medical emergency and requires immediate treatment.
Explosive Rhabdomyolysis. Explosive rhabdomyolysis is severe muscle break down in which the result is the release of muscle contents into the bloodstream. Muscle contents such as myoglobin can cause kidney damage and ultimately kidney failure.6 Untreated explosive rhabdomyolysis can be fatal.
Splenic Infarction. Splenic infarction can occur in athletes with sickle cell trait, particularly at high altitudes. Vigorous exercise at altitudes higher than 5,000 feet may increase risk. Splenic infarction causes pain in the lower left side of the chest and upper left quadrant of the abdomen. The athlete may experience nausea and vomiting as well. Athletes should consult a physician immediately if signs and symptoms occur as well as for return to play protocol.1
Managing the condition
Physically active individuals with sickle cell trait should be knowledgeable of their condition and take precautions (see list below). Physically active students in elementary, middle or high school should take precautions with physical education class and participating in sports. See our sickle cell trait action plan for help preparing for school and sports:1,3
The National Athletic Trainers’ Association task force recommends confirming sickle cell trait status (positive or negative) in all athletes’ pre-participation physical exams.7 Knowledge of the trait in athletes can help athletes, coaches and health care professionals to simple precautions that enable athletes to thrive in sports while preventing the risk of exertional sickling.
Currently, the National High School Federation has no recommendations for screening athletes for sickle cell trait. The mandated pre-participation physical should have a question about the athlete’s sickle-cell status. Sickle cell status is tested at birth and the results may be able to be found in state newborn screening records and/or with your primary care provider. Currently, no medical organization is calling for universal screening for SCT before participating in sports.8