Comprehensive analysis of sickle β⁺-thalassemia genotypes and their associated HbA levels in France

We retrospectively reviewed the clinical records of 228 HbS/β⁺-thal patients. The different genotypes were distributed into three groups according to their mean residual HbA levels: <10 % (group 1; n = 22), between 10 and 20 % (group 2; n = 175) and > 20 % (group 3; n = 31). Routine red blood cells and hemoglobin parameters were compared between the three groups. Sixteen different sickle β⁺-thal genotypes were identified but only four of them were associated with a residual HbA level below 10 %. Patients of this group exhibited a more severe anemia (Hb < 10 g/dL; reticulocytes >200 G/L) compared to the two other groups. However, no difference could be observed on those parameters between patients of group 2 and 3, as well as for the main RBC parameters. According to our study, >80 % of the sickle β⁺-thalassemia patients in France have a residual HbA level beyond 10 % and a mild to moderate anemia. Only four β⁺-thal variations (all affecting the splicing process) would lead to a potentially severe SCD syndrome in association with HbS (HbA < 10 %) but this result should be confirmed in a prospective clinical study.