GSTM1 and thalassemia: The overall prevalence of α0-thalassemia, β-thalassemia, Hb E, and α+-thalassemia (− α3.7, − α4.2,αCSα,·αPSα) were 3.5% (95%CI; 2.2–4.9), 0.8% (95%CI; 0.2–1.5), 47.7% (95%CI; 40.0–51.4), and 53.6% (95%CI; 50.0–57.3), respectively.