The stratified analyses for anemia criteria according to the IDA definition yielded pooled OR estimates of 1.84 (95% CI=1.02 to 3.33; z=2.04; P=0.04) [I2=92.7; P<0.001; tau2=0.81] for 10 studies with anemia criteria according to iron status and 1.26 (95% CI=0.73 to 2.1; z=0.84; P=0.4) [I2=84.6; P<0.001; tau2=0.63] for 11 studies with anemia criteria according to Hb and hematocrit (Hct). The gene discussed is GSTM1; the disease is anemia.