GSTM1 and thalassemia: For all patients, the mean Hb concentration was 10.1 g/dL (95% CI: 9.9-10.2) and was significantly lower in: (i) younger age groups: 8.1 g/dL < five years, 8.7 g/dL five to 14 years, and 10.4 g/dL >15 years (P <0.001), (ii) females 9.1 g/dL vs males 10.5 g/dL (P <0.001), (iii) severe (Class I and II) G6PDd: 10.0 g/dL vs 10.7 g/dL for mild/normal G6PD, P = 0.004), (iv) patients with homozygous E: 8.8 g/dL vs 10.2 g/dL (normal profile) and vs 10.1 g/dL heterozygous HbE/heterozygous HbE and α-or β-thalassaemia (P <0.001).