GSTM1 and anemia (phenotype): Consistently, as a dichotomous variable defined as the below/above cutoff for anemia, we observed a positive correlation between serum Hb and kidney disease progression in IgAN (unadjusted HR = 2.12, 95% CI = 1.44–3.12, I2 = 79%; adjusted HR = 1.65, 95% CI = 1.20–2.27, I2 = 0%).