Description:
<jats:p><jats:bold>Abstract </jats:bold> Diagnosis of hepatitis C virus infection (HCV) is based on HCV antibody testing by standard serological tests and immunoblot assays for confirmation in special cases. Differentiation of past and ongoing hepatitis C is performed by detection of HCV core antigen and HCV RNA. Ongoing hepatitis C can be assigned to infection with one or multiple HCV sub‐ and genotypes by characteristic sequence differences. Infection with HCV genotype 2 or 3 is the best pretreatment parameter for prediction of sustained virologic response to interferon‐alfa based antiviral therapy. During antiviral therapy, the key to assess virologic treatment response is quantitative measurement of HCV RNA. A decline of HCV RNA concentration from baseline to week 12 of less than 2 log steps or an absolute viral load above 30.000 IU/mL in genotype 1 infected patients is strongly associated with viral non‐response. For estimation of early virologic response on the basis of HCV core antigen measurement positive detection of core antigen at week 12 was correlated with virologic non‐response. At week 24 of treatment, at the end‐of‐therapy and during follow‐up highly sensitive HCV RNA detection assays are critical for discontinuation of further therapy and correct estimation of virologic response. Mutational analysis of different HCV regions (hypervariable region 1, non‐structural protein 5A) may provide additional information about sensitivity/resistance to interferon‐based antiviral therapy but have not yet introduced into clinical practice.</jats:p>