Importance of viral load in hepatitis C

摘要

This review analyses the usefulness of HCV RNA measurements (viral load) in patients with chronic hepatitis C.HCV infects 2-3% of the world population.It is a RNA virus,classified into at least 11 genotypes and 100 subtypes.In an HCV infected patient,HCV exists as a mixture of genetically distinct viral variants or quasi-species.Several commercial assays are able to quantify HCV RNA including branched DNA technology (signal amplification,Bayer Diagnostics~R),PCR (Roche Diagnostics~R),NASBA (Biomerieux~R),TMA (Chiron~R) and more recently real time PCR.Measurement of HCV viral load is useful in different situations.Treatment of chronic hepatitis C using Interferon-based regimens have been increasingly effective during the last decade,with about half of the patients who will eradicate the virus,identified by a sustained virological response or SVR using the Pegylated-Interferon (PEG-IFN) combined to Ribavirin.Today,RNA detection and quantification are the only systems for pre-therapeutic and therapeutic follow-up of HCV-infected persons undergoing treatment.Measures of HCV RNA before and at 12 weeks of treatment are used to determine early decrease of viral load during treatment.A 2 log HCV RNA variation is considered as a reference to manage treatment for HCV-infected persons,and patients with no significant decrease of viral load may stop treatment.Recent studies have showed that earlier viral load measurement (after 4 weeks of treatment) is also able to predict the long term response.Viral load measurement is also used to assess the infectiveness,ie.after blood exposure or to evaluate the risk of HCV transmission from a HCV infected mother to her baby.