In contrast, individuals with ß-thal major, with the genotype of β+/β0 or β0/β0 and severe anemia (Hb persistently <70 g/L), require regular blood transfusions and standardized iron-free therapy to survive (Writing Group For Practice Guidelines For Diagnosis And Treatment Of Genetic Diseases Medical Genetics Branch Of Chinese Medical Association et al., 2020). Here, GSTM1 is linked to anemia (phenotype).