Therefore, in this case, the distribution is binary; or classified as Hb < 7.0 g/dL as severe anemia, 7.0 g/dL ≤Hb≤9.9 g/dL as moderate anemia, 10.0 g/dL ≤Hb≤10.9 g/dL as mild and Hb ≥11.0 g/dL as non-anemic and in this case multinomial or an ordered categorical response is considered. This evidence concerns the gene GSTM1 and anemia (phenotype).