GSTM1 and thalassemia: The prevalence of β-thalassemia trait, Hb E trait, homozygous Hb E, and α-thalassemia 1 trait in Southern Thai couples was 2.22%, 12.08%, 1.11%, and 3.06%, respectively, and among Thai population; Southern Thai population was found to have the lowest prevalence of thalassemia and Hb E [18].