(a) Types of response to antiviral therapy Depending on the observed indicators, they can be divided into biochemical response, virological response and histological response. 1. Biochemical response: ALT and AST return to normal. Virological response: (1) Early virological response (EVR): It refers to negative serum HCV RNA qualitative test (or quantitative test less than the minimum detection limit) or quantitative test reduced by 2 log levels (Log) or more at 12 weeks of treatment. Those with early EVR are prone to obtain SVR, while those without EVR are less prone to obtain SVR, so EVR can be used as a predictor of SVR. (2) End-of-treatment virological response (ETVR): i.e., negative HCV RNA by qualitative testing at the end of treatment (or quantitative testing less than the lowest detection limit); (3) SVR: i.e., negative HCV RNA by qualitative testing at the end of treatment with at least 24 weeks of follow-up (or quantitative testing less than the lowest detection limit); (4) No response (NR): refers to those who have never obtained EVR, ETVR and SVR (4) Non-responder (NR): refers to those who never obtained EVR, ETVR and SVR (5) Relapse: HCV RNA is negative at the end of treatment (or quantitative detection is less than the minimum detection limit), but HCV RNA becomes positive again after stopping the drug; (6) Breakthrough: HCV RNA load was lowered or turned negative during the treatment, but HCV RNA load increased or turned positive before stopping the drug. 3.Histological response: It refers to the improvement of liver histopathological inflammation necrosis and fibrosis, which can be evaluated by the common liver tissue grading (degree of inflammation necrosis), staging (degree of fibrosis) or semi-quantitative scoring system at home and abroad. (B) Factors influencing response to antiviral therapy Response to antiviral therapy for chronic hepatitis C is influenced by a variety of factors, the following factors are conducive to achieving SVR: (1) HCV genotype 2 or 3; (2) viral level <2×106 copies/ml; (3) age <40 years; (4) female; (5) short duration of HCV infection; (6) mild liver fibrosis; (7) good compliance with treatment; (8) good compliance with treatment (8) no significant obesity; (9) no combined HBV and HIV infection; (10) treatment: PEG-IFNα in combination with ribavirin is the best.