GSTM1 and anemia (phenotype): Interestingly, anaemia is only prevalent in 57.1 and 25.9% of β-thalassemia carrier IVS1nt5 (c92 + 5G > C) and HbE (c.79G > A) variants, respectively, indicating that most individuals have normal Hb or are non-anaemic, though they have low SLI.