Definitions of Response

Treatment response can be measured biochemically (by normalization of serum alanine aminotransferase [ALT]), virologically (by reduction in serum HCV RNA), and histologically (by reduction in liver inflammation or fibrosis on posttreatment liver biopsy). Virologic response is the most common way to evaluate the effectiveness of HCV treatment. Biochemical and virologic responses are usually associated with histologic improvement. Given the invasiveness of liver biopsy, repeat liver biopsy following therapy is not recommended as part of routine care.

Treatment end points are generally defined as (see table):

• Rapid virologic response (RVR): HCV RNA <50 IU/mL at 4 wk into treatment.
• Early virological response (EVR): ≥2 log₁₀ reduction from baseline HCV RNA at 12 wk of treatment.
• End-of-treatment response (ETR): undetectable HCV RNA at the completion of treatment.
• SVR: undetectable HCV RNA at 24 wk after completion of treatment.
• Relapse: undetectable viremia during and/or at the end-of-treatment but virus is detectable after treatment is stopped.
• Nonresponse: detectable HCV RNA throughout treatment.