A presumptive diagnosis of the two diseases can be made by Hb analysis: in HbE-β0 thalassemia, βA-globin chains are not synthesized, and the condition is characterized by the production of HbE and HbF without detectable HbA; HbE constitutes 30–70% of the hemoglobin with the remainder HbF. This evidence concerns the gene GSTM1 and thalassemia.