EPO and anemia (phenotype): HCV-infected patients who were treated with PEG-IFN/RBV appeared to have inappropriately low levels of endogenous EPO for their degree of anaemia.31 Although serum levels of endogenous EPO increased during the combination treatment, the haemoglobin level did not return to normal, suggesting that the increase in endogenous EPO was not sufficient to fully compensate for the degree of anaemia.32 In addition, even though EPO is synthesized primarily in the kidney, other organs, such as the liver and brain, also produce it.