In addition, the median Hb in our newly onset IDA group of the training set at baseline was 131.0 g/L, which was on par with the pre-operative Hb level of patients developing postoperative anemia in the SG cohort present in the study by Ben-Porat et al. Therefore, it might be necessary to prevent the development of IDA in a premenopausal patient with an Hb level of around 130 g/L before SG. This evidence concerns the gene GSTM1 and anemia (phenotype).