Baseline Hb level, parasitemia level, G6PD deficiency, and thalassemia explained 45.4% (R2 = 45.4%) of the change in absolute Hb level (Table 2), and a higher level of G6PD enzyme activity was associated with a lower change in absolute Hb level (data not shown). This evidence concerns the gene GSTM1 and thalassemia.