Virological tools to diagnose and monitor hepatitis C virus infection.

Approximately 200 million people are chronically infected with hepatitis C virus (HCV). Infection with HCV is curable by therapy, with the current standard treatment based on the combination of pegylated interferon-α and ribavirin. Viral eradication is achieved in approximately half of treated patients. In 2011 a new antiviral treatment based on a triple combination with a protease inhibitor will become available. Virological tools are essential to diagnose HCV infection but they have found their principal application in guiding treatment decisions and assessing the virological responses to therapy. These include the anti-HCV antibody assay, measurements of HCV core antigen and HCV viral load and HCV genotyping. The HCV RNA can be ideally assayed by a real-time assay with a limit of detection of 10-15 IU/mL. Monitoring of viral kinetics during the early phases of antiviral treatment is crucial in making treatment decisions such as early stopping rules and also in optimizing the treatment duration. The HCV genotype should be assessed before the start of treatment because it determines the treatment length and ribavirin dose and also offers prognostic information on treatment outcomes as certain genotypes respond more favourably to treatment.