The Hematologist

September-October 2017, Volume 14, Issue 5

Another Myth About Sickle Cell Trait Bites the Dust

Michael DeBaun, MD, MPH Professor of Pediatrics and Medicine, Director of the Vanderbilt-Meharry Center for Excellence in SCD
Vanderbilt University Medical Center, Nashville, TN

Published on: August 14, 2017

Liem RI, Chan C, Vu TT, et al. Association among sickle cell trait, fitness, and cardiovascular risk factors in CARDIA. Blood. 2017;129:723-728.

Despite showing no increase in mortality rate for Black soldiers with sickle cell trait (SCT) participating in basic training after universal precautions were implemented, and only a small increment in exertional rhabdomyolysis,1 a lingering perception exists that SCT is associated with common morbidities. To address the health concerns of African American athletes, in 2010, the NCAA implemented a mandatory edict that all Division I football players receive SCT testing. Based on the available evidence at the time, ASH convened a committee in 2012 to evaluate the evidence for the association between SCT and adverse outcomes during rigorous exercise. The ASH committee recommended the implementation of universal interventions to reduce exertion-related injuries and deaths, concluding that this approach could be effective for all athletes, irrespective of their sickle cell status. Also, this would reduce the potential stigma of identifying athletes with SCT for distinct non–evidence-based conditioning regimens. The conclusions of the committee were described in ASH’s statement on screening for SCT and athletic participation.

Dr. Robert I. Liem and colleagues took an innovative approach when interrogating a pre-existing data set to test the hypothesis that the presence of SCT is associated with changes in fitness and risk for hypertension, diabetes, and metabolic syndrome. The team evaluated the Coronary Artery Risk Development in Young Adults (CARDIA) study, a cohort with 25 years of follow- up of patients including 1,995 African Americans. SCT was present in 6.8 percent of the African-American population (136 of 1,995), and in the course of 25 years, 46 percent (738 of 1,590), 18 percent (288 of 1,631), and 40 percent (645 of 1,611) of all participants developed hypertension, diabetes, and metabolic syndrome, respectively. However, the presence of SCT when compared to those without SCT was not associated with any of the assessed morbidities, including exercise duration p=0.62), estimated metabolic equivalent of tasks (p=0.80), maximum heart rate (p=0.41), and heart rate at two minutes recovery (p= 0.28). Using multivariable analysis, the research team did not find any evidence that SCT was associated with an increased hazard ratio of hypertension (hazard ratio, 1.22; 95% CI, 0.91-1.65; p=0.19), diabetes (hazard ratio, 1.48; 95% CI, 0.96-2.27; p=0.08), or metabolic syndrome (hazard ratio, 1.26; 95% CI, 0.92-1.74; p=0.15).

For young adults with SCT, the absence of significant medical morbidities such as chronic cardiovascular disease, diabetes, or metabolic syndrome should not be misinterpreted to mean that a diagnosis of SCT is irrelevant to affected individuals. In fact, knowledge of the presence of SCT should initiate a series of formal preconceptual genetic counselling sessions about the risk of the affected individual bearing children with sickle cell disease (SCD). These discussions should be documented in electronic medical records for future reference, for family planning, and for the assessment of rare medical complications associated with SCT such as traumatic hyphema, renal medullary carcinoma of the kidney, and splenic infarct. A glaring omission in the two African American cohort studies with 47,944 soldiers and 1,990 young adults is the lack of mention as to whether detection of SCT leads to formal preconceptual genetic counseling for those affected. Despite noteworthy advances in the care of individuals with SCD, including hematopoietic stem cell transplantation, and now gene therapy, the unanswered public health challenge (both in the United States and internationally) is how to effectively educate individuals with SCT about their risk of having children with SCD. One hundred years after discovery of SCD in modern medicine, we still await evidence-based strategies for informing individuals about SCT in a way that is culturally sensitive and informative about the risks of having a child with SCD.

References

  1. Kark JA, Posey DM, Schumacher HR, et al. Sickle-cell trait as a risk factor for sudden death in physical training. N Engl J Med. 1987;317:781-787.

Conflict of Interests

Dr. DeBaun indicated no relevant conflicts of interest. back to top