GSTM1 and anemia (phenotype): Gender (P = .003, B = −3.468, odds ratio [OR] = 0.031, 95% confidence interval [CI] = 0.003-0.297), the use of ascorbic acid (P = .002, B = 2.157, OR = 8.643, 95% CI = 2.193-34.063), and preoperative Hb (P < .001, B = −2.099, OR = 0.123, 95% CI = 0.049-0.304) had a significant effect on the development of postoperative anemia.