For a patient with chronic hepatitis C being treated with antivirals, what investigation best assesses the response to treatment?

The most effective way to assess the response to treatment in a patient undergoing antiviral therapy for chronic hepatitis C is through measuring the HCV viral load. This test quantifies the amount of hepatitis C virus in the bloodstream and is crucial in determining whether the antiviral therapy is successfully suppressing the virus.

A decrease or undetectable level of HCV RNA during and after treatment is directly correlated with a successful response to therapy. This response is monitored through specific points in the treatment timeline, such as at 4 weeks, 12 weeks, and at the end of treatment. Sustained virological response (SVR) is defined as an undetectable HCV RNA level 12 weeks after completing the treatment, indicating that the virus has been eradicated.

While anti-hepatitis C antibody concentration is used for diagnosis, it does not provide real-time information on viral replication or treatment efficacy. Liver biopsy, although useful for assessing the extent of liver damage, does not directly measure the effectiveness of antiviral therapy. Serum alanine aminotransferase (ALT) levels can indicate liver inflammation but are not specific for assessing viral response. Therefore, monitoring HCV viral load is the most reliable choice for evaluating the effectiveness of antiviral treatment in patients with chronic hepatitis C.