GSTM1 and anemia: However, the proportions of severe anemia (Hb < 8.5 g/dL) which warranted temporary RBV discontinuation were low (6.9% and 6.1%) in weight-based and flat-dose RBV arms, respectively, implying that by careful monitoring the on-treatment hemoglobin levels and titrating the RBV dosages, most patients receiving weight-based or flat-dose RBV may safely complete treatment.