Kinetics of the hepatitis C virus during interferon therapy as a marker oftherapeutic response

Background: The viral load and subtype of hepatitis C virus (HCV) are predi ctors of the efficacy of interferon (IFN) therapy. The kinetics of HCV duri ng IFN therapy have been described recently, suggesting that HCV infection is highly dynamic. These observations have raised the issue as to whether e arly monitoring of the viral load can help guide IFN therapy. Methods: We measured HCV-RNA levels at 0, 24 and 48 h after the start of IF N-alpha treatment (10 MU daily for 2 weeks and then three times weekly for 22 weeks) or IFN-P treatment (6 MU daily for 6 weeks). Then we analyzed the relationship between HCV kinetics and therapeutic response using stepwise multivariate logistic regression analysis. Results: The exponential decay slope of the viral load during the first 24, h, not the first 48 h or the next 24 h, was a predictor of viral eradicati on at 6 months after completion of the treatment (sustained response; P = 0 .0023). This decay slope was not affected by the HCV serotype or the type o f IFN used. Initial viral load and HCV serotype were also predictors, as re ported previously (P < 0.0001 and P = 0.0347, respectively). We also propos ed a model using a prognostic index that predicted a sustained response wit h more than 80% sensitivity, specificity and efficacy in an independent and external group of patients. Conclusion: This study demonstrated that the exponential decay slope of the viral load during the first 24 h was an important predictor of the respons e to IFN therapy as well as the initial viral load and HCV serotype. The mo del may also be useful for the clinical management of IFN therapy. (C) 2001 Blackwell Science Asia Pry Ltd.