Hepatitis B virus (HBV) is an enveloped, double- stranded DNA virus belonging to the Hepadnaviridae family and is recognized as the major cause of blood transmitted hepatitis together with hepatitis C virus (HCV). Infection with HBV induces a spectrum of clinical manifestations ranging from mild, inapparent disease to fulminant hepatitis, severe chronic liver disease, which in some cases can lead to cirrhosis and carcinoma of the liver. Classification of a hepatitis B infection requires the identification of several serological markers expressed during three phases (incubation, acute and convalescent) of the infection. Now several diagnostic test are used for screening, clinical diagnosis and management of the disease.
Hepatitis B “e” antigen is a virus protein to be intimately associated with hepatitis B virus replication, indicating high degree of infectivity. HBeAg appears shortly after HBsAg and is detectable for few days to several weeks. During treatment and recovery, the titer of HBeAg declines and is replaced by the corresponding antibody (anti-HBe). In chronic hepatitis B infections, elevated levels of HBeAg can be detected for years, which is a marker for large quantity of virus. In some chronic HBsAg positive patients, HBeAg is undetectable due to HBV mutations suggesting for low level of viral replication. If HBeAg is considered a specific marker of infectivity, the presence of anti-HBeAg antibody in blood is recognized to be a clinical sign of recovery from the infection.