A large cohort of β+-thalassemia in Thailand: Molecular, hematological and diagnostic considerations

We report the molecular and hematological characteristics associated with a large cohort of β+-thalassemia in Thailand. Study was done on 21,068 unrelated subjects referred to our center in northeast Thailand for hemoglobinopathies investigation. Among 21,068 subjects, 2637 (12.5%) were found to carry β-thalassemia. Of these 2637 cases, 705 (26.7%) carried β+-thalassemia with eight different mutations including 6 promoter mutations; NT-28 (A–G), NT-31 (A–G), NT-50 (G–A), NT-86 (C–G), NT-87 (C–A) and NT-90 (C–T) and two missense mutations; Hb Malay (codon 19; AAC-AGC) and Hb Dhonburi (codon 126; GTG-GGG). Hematological features of carriers with these β+-thalassemia (n = 528) were compared with those with β0-thalassemia (n = 309). Data for Hb E-β+-thalassemia (n = 177) were also presented along with Hb E-β0-thalassemia in our series (n = 94). All patients with Hb E-β+-thalassemia were associated with mild thalassemia intermedia phenotypes. Most of the β+-thalassemia carriers had elevated Hb A2 and mild hypochromic microcytosis, some demonstrated borderline MCV and MCH values which, could compromise carrier screening. Analysis of α/β-globin mRNA ratio in representative cases with normal, Hb E trait, β+-thalassemia trait, Hb Dhonburi trait and β0-thalassemia trait demonstrated the average values of 1.1, 1.7, 2.1, 1.7 and 3.1, respectively which is helpful in identification and differentiation of the cases.