GSTM1 and anemia: When the studied population was divided on the basis of the severity of anemia into two groups (Group A: very severe anemia with Hb < 4 gm/dL and Group B: severe anemia with Hb ≥ 4 gm/dL but <7 gm/dL), most of the outcomes were much worse for group A, with a statistically significant difference.