Postoperative anemia is further exacerbated by surgical blood loss (Abu-Zaid et al., 2021; Zhou et al., 2023), necessitating hemoglobin (Hb) levels ≥8 g/dL to reduce the risk of mortality (Musallam et al., 2011; Cata, 2015; Moncur et al., 2021; Shander et al., 2023; Aoyama et al., 2024). The gene discussed is GSTM1; the disease is anemia (phenotype).