[Diagnosis of Hepatitis B and C: current aspects]

The genetic variability of hepatitis B virus (HBV) is for a DNA virus extremely high. Escape mutants of the pre-core/core gene and S-gene are of clinical and diagnostic importance. HBeAg negative (pre-core) mutants are frequently associated with a more severe prognosis of chronic hepatitis B. One amino acid substitution in the neutralizing epitope of HBsAg is responsible for the failure of active and passive immunization against HBV. S-Gen mutants may be not detected with monoclonal HBsAg tests. Hepatitis C virus (HCV) is even more heterogenous than HBV. At least 6 genotypes may be differentiated. Genetic variability is the cause of reinfections, which in general have a better prognosis than primary infection. Diagnosis of infections with genotypes 4 to 6 is not absolutely reliable. The influence of different genotypes on disease progression needs to be further investigated. A more severe prognosis and higher HCV RNA concentrations are observed in genotype 1b infections. The higher RNA concentration is partly due to an in vitro artefact, since the amplification rate with current primer pairs is optimal for genotype 1.