The predictors of anemia that we identified in the context of interferon-free treatment can help clinicians identify patients who may need to be monitored more closely during ribavirin-containing, interferon-free therapy, including patients with advanced age, low baseline hemoglobin, or with the ITPA-non-deficient genotypes at both the rs1127354 and the rs6051702 positions. Here, ITPA is linked to anemia.