Predictive factors of a response to interferon therapy in chronic hepatitis C.

To determine predictive factors of response to interferon (IFN) therapy in chronic hepatitis C patients, we administered IFN-alpha, 1 6 million U1 intramuscularly daily for 2 consecutive weeks, then three times a week, to 136 patients judged to have chronic hepatitis C virus (HCV) infection according to HCV-RNA positivity. We also investigated the most effective length of IFN-alpha treatment according to efficacy factors, i.e., histological activity index. HCV-RNA genotype, and HCV-RNA levels. patients were classified either into a short-term group (entire treatment period 16 weeks), standard-term group (24 weeks), and long-term group (40 weeks). Patients were assessed as complete responders (CR) if their HCV-RNA became negative and their alanine aminotransferase (ALT) decreased to < or = 39 IU/L after 18 months of treatment or nonresponders in other cases. Results showed that HCV-RNA levels and genotype were statistically significant predictive factors. CR rates in the standard- and long-term groups were significantly higher than in the short-term group (p < 0.05). In patients with low HAI scores, the long-term group showed the highest CR rate. In patients with low virus counts, the CR rate increased to 73% in the 24th week and 100% in the 40th week. CR rates in patients with HCV-RNA genotype 1b and 2a or 2b also increased as the treatment period became longer. For efficacy, a 24-week treatment period was necessary. In patients with mild liver tissue damage or low virus counts, 40 weeks of treatment proved highly useful.