Viral factors affecting the outcome of therapy for chronic hepatitis C.

The advent of sensitive virologic assays to quantify hepatitis C virus (HCV) RNA and to differentiate specific genotypes of HCV has greatly expanded our understanding of the pathogenesis of chronic hepatitis C. These molecular virologic techniques are regularly employed to assist with management decisions regarding antiviral therapy. Genotype is the strongest predictor of a sustained virologic response (SVR). The dynamic change of HCV RNA during treatment, defined at week 12 as early virologic response (EVR), is useful for identifying individuals who are unlikely to have an SVR. Discontinuation of therapy can be considered for those patients with genotype 1 when an EVR is not achieved. However, limitations exist regarding interpretation of EVR and treatment decisions must be individualized, particularly when other endpoints of therapy, such as histological response or treatment of extrahepatic manifestations are being considered.