Multivariate analysis identified several independent predictors of transfusion requirements, including advanced age (>65 years, OR 2.4), preoperative anemia (Hb <10 g/dL, OR 3.2), prolonged surgical duration (>3 hours, OR 2.1), and substantial intraoperative blood loss (>500 mL, OR 4.0). The gene discussed is GSTM1; the disease is anemia (phenotype).