The α-thalassemia-1 (α-thal-1) Southeast Asian (- -(SEA)) type deletion, β-thalassemia (β-thal) and Hb E [β26(B8)Glu→Lys, GAG>AAG] are the most common genetic disorders in Southeast Asian populations. Mean corpuscular volume (MCV) <80.0 fL with normal hemoglobin (Hb) is used for screening α- and β-thal, and a Hb E level of less than 25.0% is used for predicting α-thal-1 in Hb E trait. Thus, levels of Hb, MCV and Hb A(2)/E were reviewed and compared between the SEA type deletion co-inherited with β-thal trait (n = 61), with Hb E trait (n = 102) or homozygous Hb E (n = 13) and β-thal trait (n = 636), Hb E trait (n = 544) or homozygous Hb E (n = 83), respectively. When comparing the values of all three analyzed hematological parameters, only the - -(SEA)/β(E) values were shown to be significantly lower than those of Hb E trait. Furthermore, at a cut-off value of Hb A(2)/E of 21.54%, 95.0% of the - -(SEA)/β(E) had Hb A(2)/E levels lower than this cut-off value, while 94.0% of Hb E trait had Hb A(2)/E at higher levels. Accordingly, the Hb A(2)/E level at 21.54% is the best indicator for predicting co-inheritance of the α-thal-1 - -(SEA)/ deletion and Hb E trait.