Several factors are potential predictors for treatment response with PEG-IFN-α based regimen and may improve predictive efficiency of IL-28B genotype for treatment outcome in CHC-infected patients, including baseline γ-glutamyltransferase/alanine aminotransferase ratio, vitamin D level, serum ferritin concentration, and early anemia. The gene discussed is GPT; the disease is anemia (phenotype).