GSTM1 and anemia (phenotype): Group 1; Hb > 10.1 gm/100ml (control group), Group 2; Hb= 8.1-10 gm/100ml (mild anemia) Group 3; Hb= 6.5-8 gm/100ml (moderate anemia) Group 4; Hb <6.5 gm/100ml (severe anemia).