Tuesday, June 11, 2013

Sickle Cell Trait: What You Need to Know

As previous blogs have demonstrated there are a variety of conditions that can be of concern and potentially fatal if not treated quickly by trained professionals.  Some of the topics discussed include  sudden cardiac arrest, infectious mononucleosis, exertional heat illness, an asthma attack, and diabetic emergencies among others.  The topic I am going to discuss today is another one of those topics, sickle cell trait (SCT).  Understanding SCT is particularly important for certain segments of the population as it is more common in certain ethnic groups.  Additionally, exertional sickling and sickling collapse, an emergency condition that can result during intense exercise may sometimes be mistaken for exertional heat illness (EHI).  My goal today is to define SCT, differentiating it from sickle cell disease (SCD), provide you key identifiers that differentiates SCT from EHI (most often heat cramps) and provide a brief introduction to the mandated NCAA testing policy.

SCT is present in those people who inherit one sickle cell gene and one normal gene (CDC).  SCT can be diagnosed with a simple blood test; infants in the United States are tested at birth.  SCT is different from sickle cell disease (SCD) because SCD requires the inheritance of two abnormal genes, one from each parent.  This gene results in the mutation of hemoglobin cells, causing them to take on a crescent or sickle shape (see image below) and making it more difficult for these cells to transport oxygen.

SCT affects 1 in 12 African Americans, but the condition can also be prevalent in those with ancestry from South American, the Caribbean, Central American and Mediterranean countries including Saudi Arabia, India, Turkey, Greece and Italy. As parents, it may be important that you ask for the results of this test for your new infant.  Despite the required testing most people do not know their sickle cell trait status unless they have sickle cell disease.  People are typically asymptomatic, but there can be potential for complications when the following conditions/situations are present:
  • Increased pressure in the atmosphere (ex. when scuba diving)
  • Low oxygen levels in the air (ex. very intense training, exertion at altitude)
  • Dehydration
  • High altitudes

As of this time, there is no recommendation that athletes with SCT should be withheld from participating in sports, however, some research has shown that athletes can be particularly at risk of complications from SCT when completing intense training.  The possibility of complications can be enhanced by training in extreme temperatures or at high altitudes (as previously mentioned).  The key to SCT is prevention is to set your own pace, rest often between drills/activities, stay hydrated before/during/after activity and keep the body as cool as possible when exercising in hot conditions according to the CDC fact sheet.

For an individual who has SCT and completing intense exercise the biggest concern is a condition called exertional sickling (and the resulting sickling collapse).  In exertional sickling the intense exercise causes normal the sickle shaped blood cells to “logjam” the blood vessels, slowing oxygen transport to the muscles.  Muscle tissue begins to breakdown after a prolonged period of a lack of oxygen resulting in a condition referred to as rhabdomyolysis.  This condition is a medical emergency and can lead to death if not treated immediately.  The biggest key to proper treatment is immediate recognition of the condition and proper treatment.  Exertional sickling/sickling collapse can sometimes be confused with exertional heat illness, particularly heat cramps.

Typically happens within first 30 minutes on the field
Typically happens after prolonged exercise for more than 30 minutes
Core temperature is not elevated
Core temperature is typically >1040F
Pain is strong and generalized
Heat cramps:  muscle twinges and focused pain
Typically slump to ground with weak muscles; sufferers will lie fairly still and muscles will look and feel normal to the observer
Heat cramps:  suffers “hobble” and muscle are locked up and hard to touch, suffers will yell out/writhe in pain

If you or your athletic trainer suspect exertional sickling the athlete should be removed from activity immediately.  Oxygen can be administered if available (and someone is trained in its use) and the EAP should be activated.  A sickling collapse is a medical emergency.

Want to know more about an athlete who’s competing in the NFL with sickle cell trait?  Check out Ryan Clark, Pittsburgh Steelers.  He has been able to have an NFL career despite being held out of recent games in Denver, Colorado given is SCT status.  Remember, exertion at high altitudes has the potential to result in exertional sickling/sickling collapse.  He has now started a foundation to search for a cure for the condition.

The National Collegiate Athletic Association (NCAA) has mandated sickle cell testing for athletes.  This requirement is considered controversial by some based on the available (or lack thereof) research, but my goal is not to debate the merits of the requirement, but to help you understand it.  If you’d like to learn more about why some people believe the mandated testing policy is unnecessary check out this article.  Testing has been mandated for Division I athletes since 2010 and Division II since 2011.  Legislation just passed that will mandate testing at the Division III level starting this year (2013).  For those of you who are concerned and do not wish to have your child tested as part of their initial college pre-participation examination there is a waiver you can sign to opt out of the testing.  Additionally, SCT positive athletes are not restricted from participating in athletics, it simply allows the medical staff to be more aware of the possibility of a exertional sickling and sickling collapse.  Testing is expected prior to the start of the freshman year, or for any transfer whose status is not known.  Remember, if you have the SCT status of your child documented at birth, additional testing prior to the entry into college may not be necessary.  Find out more information and resources from the NCAA here or contact the sports medicine staff at the college/university your child will be attending.

The documents listed here are mostly statements from various professional organizations regarding SCT trait status in athletes.  Some of the statements discuss recommendations for the safe sports participation and treatment in the instance of exertional sickling/sickling collapse.  Others discuss the need (or suggest there is no need) for SCT screening of athletes.  As always you are encouraged to take a look.

Submitted by Heather L. Clemons, MS, MBA, ATC

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