Phenotypic expression of hemoglobins A2, E and F in various hemoglobin E related disorders

Study on the phenotypic expression of hemoglobin (Hb) A2 and Hb E in Hb E disorders has been difficult due to the co-separation of Hb A2 and Hb E in most Hb analysis assays. Because these two Hbs are separated on capillary electrophoresis, we studied phenotypic expression of Hbs A2, E and F in various Hb E disorders using this system. This was done on 362 subjects with several Hb E disorders including heterozygous Hb E, homozygous Hb E, β-thalassemia/Hb E, δβ-thalassemia/Hb E, and Hb Lepore/Hb E and those of these disorders with several forms of α-thalassemia. Normal controls showed Hb A2 of 2.7 ± 0.3%. Heterozygous Hb E and homozygous Hb E had elevated Hb A2 i.e. 3.8 ± 0.3% and 4.8 ± 0.5%, respectively. Further elevations were observed for β0-thalassemia/Hb E (6.1 ± 1.9%) and β+-thalassemia/Hb E (7.1 ± 1.2%). Interestingly, no elevation of Hb A2 was found in the δβ-thalassemia/Hb E, and Hb Lepore/Hb E (2.3 ± 0.3%) but higher Hb F levels were noted which could be useful diagnostic markers. The levels of Hb E were variable. Co-inheritance of these Hb E disorders with α-thalassemia were associated with lower outputs of Hb E and Hb F but the levels of Hb A2 were not altered. Different phenotypic expression of Hb A2, Hb E and Hb F could help in differential diagnosis of these Hb E related disorders commonly encountered in the regions where access to molecular techniques is limited.