GSTM1 and malaria: The mean (standard deviation) Hb concentration at the end of the malaria transmission season was similar in the two treatment groups; 10.2 (1.6) g/dL in the SP/AQ group compared to 10.3 (1.5) in the placebo group, difference adjusted for baseline Hb 0.04 (95% CI -0.09, 0.17; P = 0.55).