What is the sickle cell trait (SCT)?

Updated: May 12, 2021
  • Author: Joseph E Maakaron, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Sickle cell trait is the heterozygous carrier state of HbS. These individuals have approximately 40% HbS and 60% HbA, less so with coexisting alpha-thalassemia trait.

People with sickle trait generally are well and have the following characteristics:

  • Normal life expectancy

  • Not at excessive risk for infection

  • Not subject to painful crisis under normal circumstances

  • No anemia

Nevertheless, providing genetic counseling to prospective parents with sickle cell trait is important. Reports exist of excessive deaths under extreme conditions, such as military basic training involving strenuous exertion; however, this is very uncommon. Similarly, isolated reports exist of organ infarction and crisis under unusual circumstances. Many of these patients lose urine-concentrating capacity. Painless hematuria may be present.

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