Laboratory diagnosis of hepatitis B virus infection by nucleic acid hybridization analyses and immunohistologic detection of gene products.

The laboratory diagnosis of hepatitis B virus (HBV) infection is based on two types of analyses: (i) Immunochemical detection in serum or liver of viral antigens or their respective antibodies; (ii) Demonstration of HBV DNA in serum or liver by nucleic acid hybridization techniques (dot and transfer blots, in situ hybridization). These hybridization analyses have proven to be more sensitive than immunochemical assays for the detection of viral markers and have revealed HBV DNA in serum and liver of patients without serologic evidence of HBV infection. With appropriate controls, probes and hybridization conditions the hybridization assays are exquisitely specific. They are particularly useful in studying the molecular biology of the virus, its extrachromosomal replication or integration into the cellular genome and transformation of the infected hepatocytes. Further, recent studies have identified new target cells for HBV in liver (bile duct epithelial cells, endothelial cells, smooth muscle cells in blood vessel walls), spleen, bone marrow and white blood cells. While serological and immunohistochemical assays are still the basis of routine laboratory diagnosis of HBV infection, nucleic acid hybridization provides novel information useful in establishing the etiology of certain cases of viral hepatitis without serologic evidence for known viral agents (so-called non-A, non-B hepatitis), for demonstrating active viral replication in infected individuals, and for selecting and monitoring patients undergoing antiviral therapy.