Upon analysis of the data from the combined 3 cohorts, among the 18 662 patients (2.3%) who received an intraoperative pRBC transfusion, 6610 (35.4%) did not have anemia, 8529 (45.7%) had mild preoperative anemia (hemoglobin [Hb] <12 g/dL for female patients and <13 g/dL for male patients [to convert to grams per liter, multiply by 10]), 2600 (13.9%) had moderate anemia (Hb <10 g/dL to >7.5 g/dL), and 923 (4.9%) had severe anemia (Hb <7.5 g/dL). This evidence concerns the gene GSTM1 and anemia.