In the multivariate logistic regression model for an allogeneic RBC transfusion, the preoperative Hb concentration (p < 0.001), cardiovascular disease (p < 0.001), low body mass index (p < 0.001), diabetes (p = 0.001), ASA score (p = 0.001), haemophilia (p = 0.002), thrombocytes (p = 0.003), estimated glomerular filtration rate (eGFR, p = 0.004) and age (p = 0.027) were the strongest predictors. The gene discussed is GSTM1; the disease is hemophilia.