[Virologic techniques for the diagnosis and monitoring of hepatitis B]. / Les techniques virologiques de diagnostic et de suivi de l'hépatite B.

Both serologic and molecular tools are useful for the diagnosis, monitoring and therapeutic management of viral hepatitis associated with hepatitis B virus (HBV). Compared with the standard tests to detect viral antigens and the antibodies directed against them, real-time PCR techniques today make it possible to quantify viral DNA more sensitively and more precisely. They thus replace the techniques previously used in most virology laboratories. New markers, such as the HBV genotype or the amino-acid substitution profile associated with HBV resistance to nucleoside and nucleotide analogs (NRTIs), can also be characterized by techniques based on sequencing or reverse hybridization. There is not currently any consensus about the first-line treatment for chronic HBV infection. Patients with a wild-type virus (HBe antigen-positive), a moderate viral load, and elevated serum alanine aminotransferase (from 2 to 5 times the upper limit of normal) are good candidates for treatment with pegylated interferon-alpha. Patients who are HBe antigen-positive and do not respond to this first-line treatment, as well as patients with chronic e-antigen-negative hepatitis B, are candidates for prolonged treatment, probably lifelong, by nucleoside or nucleotide analogs. Whatever the HBe serologic status and treatment, the efficacy of antiviral treatment is assessed by repeated measurements of viral load and serum alanine aminotransferase levels, in principle, every 12-24 months. In patients who are HBe antigen-positive, the efficacy of antiviral treatment is shown by the loss of HBe antigen, followed by the appearance of anti-HBe antibodies (HBe seroconversion), a reduction in viral load below 2x10(4)IU/mL and normalization of serum aminotransferase. In patients who are HBe antigen-negative or HBe antigen-positive but do not seroconvert after short-term treatment and who receive nucleoside or nucleotide analogs, the treatment objective is for HBV DNA to become undetectable by real-time PCR. Nonetheless, this objective is not always met, and it is recommended that viral replication be maintained at the lowest possible level for the longest possible time (ideally, lifelong). In all cases, when a virologic response to treatment is observed (significant reduction in viral load) and is followed by a relapse characterized by a viral load augmentation of at least 1 Log(10)IU/mL relative to the nadir, viral resistance to treatment must be suspected, after treatment adherence has been verified.