Conclusion: In this study, the primary clinical considerations for prescribing a PRBC transfusion were anemia symptoms in 72.1% of patients, Hb value in 25.2% of patients, and medical history in 2.7% of patients; 47.9% (70 patients) received a transfusion at Hb ≥8.0 g/dL. This evidence concerns the gene GSTM1 and anemia (phenotype).