The group of disorders known as sickle cell disease (SCD) is one of the more common genetic hemoglobinopathies. Homozygous production of the S variant of hemoglobin (Hb) in red blood cells (RBCs) results in profound sickling under conditions of physiologic stress, a condition known as Hb SS disease. People with Hb SS disease are at risk of chronic hemolytic anemia, tissue ischemia that causes vaso-occlusive pain syndrome, and other vaso-occlusive complications.1 They also experience a > 20-year reduction in life expectancy, compared to age-matched controls; onset of risk of early death is usually after age 25 years.
People with heterozygous expression of the Hb S variant—that is, from one parent, and expression of Hb A from the other parent—are said to have sickle cell trait (SCT). They typically do not have symptoms of SCD, although they can experience vaso-occlusive pain under severe physiologic stress and suffer sudden death more often than age-matched controls. People who are heterozygous for Hb S but have another hemoglobinopathy (eg, sickle β0 thalassemia) might have milder SCD, with fewer symptoms, or might have severe sickle cell anemia (SCA).
Alleviating the harsh burden of illness. All patients with SCD are more likely than age-matched counterparts to experience income loss because of their disability; the same loss is true for their caregivers. Such loss, when combined with time spent in the health care system, can be catastrophic.2,3 But this loss can be mitigated with access to regular, comprehensive health care that includes the steps described here to detect SCD early and reduce the likelihood of complications.4,5
To begin, TABLE 16 lists typical laboratory findings and classifications in patients who are homozygous or heterozygous for Hb S, and therefore experience more severe Hb SS disease or milder SCD, respectively.
Who should be screened for hemoglobinopathy?
Because of the presence of the fetal Hb (Hb F) in newborns and infants, clinical signs of Hb SS before age 2 months are uncommon. Neonatal clinical laboratory testing is necessary for prompt identification of Hb SS; universal screening is now required by all states (although parents can opt out by claiming a religious exemption). A positive test result requires confirmatory testing: most often, Hb electrophoresis or DNA testing.
A confirmed positive homozygous (Hb SS) or heterozygous (Hb S) result is reported to the patient’s identified medical home for subsequent management. Thus, pediatric patients with SCD can be identified, and prophylactic treatment initiated, as early as possible. Later in the patient’s life, repeat screening for SCD and SCT is recommended at the initiation of pregnancy care7 and prior to the start of high-intensity physical training, as occurs in college and professional athletics and in certain branches of the military.8
Putting prevention into practice
Some of the recommendations we make to prevent complications of SCD are directed only at patients with severe disease—ie, those who have Hb SS SCD or sickle β0 thalassemia (SCA); the rest apply to all patients with SCD (TABLE 26,9). (For patients with SCT, follow guidelines as you would for patients who do not have SCD, unless otherwise noted.)
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