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Table 1 Categorization and sequelae of hemoglobinopathies examined

From: Association between sickle cell and β-thalassemia genes and hemoglobin concentration and anemia in children and non-pregnant women in Sierra Leone: ancillary analysis of data from Sierra Leone’s 2013 National Micronutrient Survey

Category Nomenclature Definition; sequelae
Normal hemoglobin (AA) or hemoglobin C trait (AC) HbAA/AC Red blood cells are normal, and individuals have no symptoms and normal hemoglobin concentrations [9, 15]
Homozygous sickle cell genes HbSS Sickle cell gene inherited from both parents, resulting in red blood cells that have a sickle shape at low oxygen tension; HbSS can result in increased under-5 mortality and maternal mortality, and hemoglobin concentrations are often around 80 g/L [9, 16]
Heterozygous sickle cell trait HbSC Heterozygous sickle cell trait, whereby individuals inherit a sickle cell gene from one parent and a hemoglobin C gene from the other parent; individuals have fewer sickle cells but may have slightly lower hemoglobin concentrations than HbAA individuals [17]. Hemoglobin C is most prevalence in West Africa [15]
Heterozygous sickle cell trait HbAS Heterozygous sickle cell trait, whereby individuals inherit a normal hemoglobin A gene from one parent and a hemoglobin S gene (i.e. sickle cell gene) from the other parent; Individuals often no symptoms and normal hemoglobin concentrations [6] and inherit partial protection against malaria [18]
β-Thalassemia β-Thalassemia An inherited mutation that results in a “reduced or absent synthesis of beta globin chains” [19]; red blood cells are smaller than usual and hemoglobin may be lower than in HbAA individuals [20]