Thus, HbE-β+-thalassemia with such phenotypes is difficult to differentiate from HbE heterozygotes by routine laboratory investigations based on hematological screening and Hb analysis, leading to misdiagnosis of the phenotype as HbE heterozygous, especially in areas where HbE and β-thalassemia are prevalent, such as Thailand. The gene discussed is GSTM1; the disease is thalassemia.