The rise in [Hb] after i.v. iron is in keeping with other perioperative studies using intravenous iron to treat anaemia (Froessler et al. 2016; Keeler et al. 2017; Kim et al. 2017; Moppett et al. 2019; Xu et al. 2019). The gene discussed is GSTM1; the disease is anemia.