Then the child can be grouped into one of three categories: (i) severe and complicated anaemia (Hb <40 g/l or Hb 40–60 g/l, with clinical severity features); (ii) Hb 40–60 g/l, without clinical severity features; and (iii) Hb >60 g/l, with or without severity signs. This evidence concerns the gene GSTM1 and anemia (phenotype).