GSTM1 and anemia (phenotype): Because the models did not converge to assess the modifying effect of IHbD type on the final prevalence of anaemia, low ferritin and high sTfR (Table 4), we investigated the impact of MNP on these prevalence in stratified analyses by those IHbD types with adequately large sample sizes (non-clinically significant IHbD, n 475; Hb E trait, n 530; β-thalassaemia trait or homozygous Hb E, n 167).