Co‐inheritance of α 0 ‐thalassemia elevates Hb A 2 level in homozygous Hb E: Diagnostic implications

Differentiation of homozygous hemoglobin (Hb) E with and without α 0 ‐thalassemia is subtle on routine hematological ground. We examined in a large cohort of homozygous Hb E if the level of Hb A 2 is helpful. Methods A total of 592 subjects with homozygous Hb E were recruited from ongoing thalassemia screening program. Additionally, five couples at risk of having fetuses with Hb Bart's hydrops fetalis who were homozygous Hb E were also investigated. Hb analysis was performed using capillary electrophoresis system. Globin genotypes were defined by DNA analysis. Results Subjects were classified into four groups including pure homozygous Hb E (n=532), homozygous Hb E/α 0 ‐thalassemia (n=48), Hb Constant Spring EE Bart's disease (n=8), and Hb EE Bart's disease (n=4). The levels of Hb A 2 were found, respectively, to be 4.97±0.69, 6.64±1.02, 4.86±0.87, and 7.60±1.04%. Among five couples at risk, α 0 ‐thalassemia was identified in three subjects with Hb A 2 >6.0%. Conclusions Increased Hb A 2 level is a useful marker for differentiation of homozygous Hb E with and without α 0 ‐thalassemia. This should lead to a significant reduction in number of referral cases of homozygous Hb E for molecular testing of α 0 ‐thalassemia in routine practice.