Hepatitis B virus - Lab diagnosis, Prophylaxis, Control

Lab diagnosis of Hepatitis B virus

The laboratory diagnosis of the Hepatitis B virus is mostly based on serodiagnosis.

Specimen

• Serum

• Liver biopsy

Serodiagnosis

Definite diagnosis of Hepatitis B virus depends on serological tests that detect either viral Ag or Ab produced by the host i.e. HbsAg, HbcAg. They indicate viral replication.

These Ag are present during viral replication. But as viral replication begins to slow down, anti-HbeAg is detected and HbeAg disappears.

HBsAg produced may persist for many years followed HBcAg (IgM) presence.

HBsAg

• HBsAg appears in blood during the Incubation period

• detectable in most patients during prodrome and acute phase of the disease

• the persistent presence of HBsAg in blood for at least 6 months indicates the carrier state and risk of chronic hepatitis as well as hepatic carcinoma

HbsAg

• HbsAg is a protective Ab that neutralizes the virus. It is usually not detectable during the acute disease, not the chronic carrier stage because it is bound to a large amount of HBsAg present in the blood

HBcAb

• The demonstration is used to confirm HBV infection

• HBcAb appears shortly after HbsAg in acute disease and persists for life

• the presence of HBcAb is present in individuals with acute, and chronic infections as well as those who have recovered from acute infections. This HbcAg IgG does not differentiate between acute, chronic, and recovery phase

• presence of HBcAb IgM is diagnostic of acute HBV infection

• HbcAg is not detectable in serum but can be demonstrated in liver cells by immunofluorescence

HbeAg

• the presence of HBcAb IgM is diagnostic of acute Hepatitis B virus infection

• HbcAg is not detectable in serum but can be demonstrated in liver cells by immunofluorescence.

Molecular diagnosis

A molecular diagnosis such as PCR for demonstration of Hepatitis B virus DNA is used to detect and monitor the treatment of chronic Hepatitis B virus infection. It is also used to identify HBV as the cause of liver infection in HBsAg- negative patients

DPA test in liver biopsy may also be done

Other tests include elevation of ALT and AST levels. i.e. 1000-2000 IU/ml in acute hepatitis

Prophylaxis, Control of Hepatitis B virus

The prophylaxis and control of Hepatitis B virus are:

• No specific antiviral treatment is available for acute HAV infection

• Therapy is recommended for chronic infections

• the supportive and symptomatic cases should be given

• Interferon and nucleoside analogs are widely used

• vaccines available