Abstract

The diagnosis of chronic hepatitis B virus (HBV) infection is made using a combination of serological, virologic, biochemical, and histologic markers. The natural history of HBV infection can be divided into four phases: immune tolerance, immune clearance (HBeAg-positive chronic hepatitis B), inactive HBsAg carrier, and reactivation (HBeAg-negative chronic hepatitis B). Patients in the immune clearance and reactivation phases, with elevated alanine aminotransferase (ALT) and HBV DNA levels, are candidates for antiviral therapy. The primary goal of therapy for chronic hepatitis B is suppression of viral replication, which has been shown to reduce hepatic necroinflammation and retard progression of hepatic fibrosis. Long-term suppression of serum HBV DNA is likely to reduce progression to cirrhosis and hepatic decompensation and decrease the risk of hepatocellular carcinoma. Current antiviral therapy for chronic hepatitis B includes interferon alfa, peginterferon alfa-2a, lamivudine, adefovir, entecavir, and telbivudine. In patients with HBeAg-positive chronic hepatitis B, antiviral treatment is indicated when the serum HBV DNA level is = or > 10(5) copies/mL (20,000 IU/mL) and the ALT level is elevated. For HBeAg-negative patients, the threshold for initiation of therapy is lower, i.e., a serum HBV DNA level = or > 10(4) copies/mL (2,000 IU/mL) in association with an elevated ALT level. The presence of at least moderate necroinflammation and the presence of fibrosis on liver biopsy, which is optional and not mandatory before therapy, may be useful in supporting the decision to initiate therapy, particularly in patients with normal ALT levels. While undergoing therapy, patients require monitoring every 3 to 6 months to ensure compliance and to test for the development of resistance if an oral agent is used. Issues that remain controversial or need to be studied further are the necessity of a baseline liver biopsy, the HBV DNA and ALT thresholds for initiation of therapy, the optimal duration of antiviral therapy, selection of one agent over another, and the role of combination therapy.

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