[Serum biological markers and screening of viral hepatitis].

The diagnosis of hepatitis A is based on IgM anti-HAV positivity. IgG anti-HAV indicates immunity from further infections of hepatitis A. In acute hepatitis B, HBs Ag is the first marker to appear in the serum, followed by HBe Ag and anti-HBc. After recovery, HBs Ag disappears, anti-HBs appears with anti-HBe and anti-HBc and persists for many years. Anti-HBs is indicative of recovery and immunity. Chronic hepatitis B infection is defined as the persistence of HBs Ag for more than 6 months. The presence of HBeAg and HBV DNA in the serum of HBsAg positive carriers has been considered as indication of active viral replication. After a variable period, often several years, viral replication disappears. The patient displays serum anti-HBe antibodies and HBV DNA is not detected in the serum. This state is the most frequently observed and has been classified as wild type. Mutations have been described. The delta virus is not able to replicate on its own, but is capable of infection when activated by the presence of hepatitis B virus. The appearance of serum IgG anti-delta is the simplest method of diagnosing delta infection. Serological tests for HCV detect antibodies to viral antigens (Elisa assay). Each positive anti-HCV assay must be followed by a complementary confirmation test. The most widely used method for supplementary testing is the recombinant immunoblot assay in which antibodies are sought for recombinant antigens of HCV coated on nitrocellulose strips.(ABSTRACT TRUNCATED AT 250 WORDS)