Virologic monitoring of hepatitis B virus therapy in clinical trials and practice: recommendations for a standardized approach.

Treatment of chronic hepatitis B virus (HBV) infection is aimed at suppressing viral replication to the lowest possible level, and thereby to halt the progression of liver disease and prevent the onset of complications. Two categories of drugs are used in HBV therapy: the interferons, including standard interferon alfa or pegylated interferon alfa, and specific nucleoside or nucleotide HBV inhibitors that target the reverse-transcriptase function of HBV-DNA polymerase. The reported results of clinical trials have used varying definitions of efficacy, failure, and resistance based on different measures of virologic responses. This article discusses HBV virologic markers and tests, and their optimal use both for planning and reporting clinical trials and in clinical practice.