GSTM1 and G6PD deficiency: The established cut-off points for G6PD deficiency for this study was 7.69 U/g Hb (60 % of 12.8 U/g Hb; the normal mean activity) and 2.56 U/g Hb for severe deficiency (20 % of normal mean activity) while the range for moderate deficiency (20 % - 60 % of normal mean activity).