In the group with confirmed anaemia, the mean value of the Hb levels detected by the portable device was lower than the mean value of the Hb levels obtained from the full blood count [11.1 g/dl (95% CI from 10.9 to 11.4) vs 11.4 g/dl (95% CI from 11.2 to 11.7), (P = 0.01)]. This evidence concerns the gene GSTM1 and anemia (phenotype).