GSTM1 and Iron deficiency anemia: Overall, compared with iron sucrose for iron deficiency anemia, iron isomaltoside showed similar change of Hb (SMD=0.14; 95% CI=-0.07 to 0.35; P=0.18), Hb responder (SMD=1.41; 95% CI=0.71 to 2.81; P=0.33), serum ferritin (SMD=15.13; 95% CI=-23.45 to 53.71; P=0.44), and transferrin saturation (SMD=1.20; 95% CI=-1.08 to 3.47; P=0.30).