GSTM1 and anemia (phenotype): This outcome data was analyzed with the random-effects model, and the pooled estimate of the four included RCTs suggested that compared to iron sucrose for anemia, iron isomaltoside showed similar change of Hb (SMD=0.14; 95% CI=-0.07 to 0.35; P=0.18), with significant heterogeneity among the studies (I2=86%, heterogeneity P=0.0001, Figure 2).