Hepatitis B laboratory tests


 * Associate Editor In Chief:

Lab Tests
The tests, called assays, for detection of hepatitis B virus infection involve serum or blood tests that detect either viral antigens (proteins produced by the virus) or antibodies produced by the host. Interpretation of these assays is complex.

The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection. It is the first detectable viral antigen to appear during infection. However, early in an infection, this antigen may not be present and it may be undetectable later in the infection as it is being cleared by the host. The infectious virion contains an inner "core particle" enclosing viral genome. The icosahedral core particle is made of 180 or 240 copies of core protein, alternatively known as hepatitis B core antigen, or HBcAg. During this 'window' in which the host remains infected but is successfully clearing the virus, IgM antibodies to the hepatitis B core antigen (anti-HBc IgM) may be the only serological evidence of disease.

Shortly after the appearance of the HBsAg, another antigen named as the hepatitis B e antigen (HBeAg) will appear. Traditionally, the presence of HBeAg in a host's serum is associated with much higher rates of viral replication and enhanced infectivity; however, variants of the hepatitis B virus do not produce the 'e' antigen, so this rule does not always hold true. During the natural course of an infection, the HBeAg may be cleared, and antibodies to the 'e' antigen (anti-HBe) will arise immediately afterwards. This conversion is usually associated with a dramatic decline in viral replication.

If the host is able to clear the infection, eventually the HBsAg will become undetectable and will be followed by IgG antibodies to the hepatitis B surface antigen and core antigen, (anti-HBs and anti HBc IgG). A person negative for HBsAg but positive for anti-HBs has either cleared an infection or has been vaccinated previously.

Individuals who remain HBsAg positive for at least six months are considered to be hepatitis B carriers. Carriers of the virus may have chronic hepatitis B, which would be reflected by elevated serum alanine aminotransferase levels and inflammation of the liver, as revealed by biopsy. Carriers who have seroconverted to HBeAg negative status, particularly those who acquired the infection as adults, have very little viral multiplication and hence may be at little risk of long-term complications or of transmitting infection to others.

More recently, PCR tests have been developed to detect and measure the amount of viral nucleic acid in clinical specimens. These tests are called viral loads and are used to assess a person's infection status and to monitor treatment.

The original assays for detection of hepatitis B virus infection involve serum or blood tests that detect either viral antigens (proteins produced by the virus) or antibodies produced by the host. Interpretation of these assays is complex. The table below is organized chronologically, from top to bottom:

A person negative for HBsAg but positive for anti-HBs has either cleared an infection or has been vaccinated previously. A number of persons who are positive for HBsAg may have very little viral multiplication, and hence may be at little risk of long-term complications or of transmitting infection to others.

More recently, PCR tests have been developed to detect and measure the amount of viral nucleic acid in clinical specimens. These tests are useful to assess a person's infection status and to monitor treatment.

Diagnostic Criteria
==Recommendations for Monitoring Patients with Chronic HBV Infection: AASLD Practice Guidelines 2009 == 1. HBeAg-positive and HBeAg-negative patients who meet criteria for chronic hepatitis B should be evaluated for treatment. (Grade I)

2. HBeAg-positive patients:
 * HBeAg-positive patients with persistently normal ALT should be tested for ALT at 3-6 month intervals. ALT along with HBV DNA should be tested more often when ALT levels become elevated. HBeAg status should be checked every 6-12 months. (Grade III)
 * Patients who remain HBeAg positive with HBV DNA levels >20,000 IU/mL after a 3-6 month period of elevated ALT levels between 1-2 ULN, or who remain HBeAg positive with HBV DNA levels >20,000 IU/mL and are >40 years old, should be considered for liver biopsy, and treatment should be considered if biopsy shows moderate/severe inﬂammation or signiﬁcant ﬁbrosis (Grade III). Patients who remain HBeAg positive with HBV DNA levels >20,000 IU/mL after a 3-6 month period of elevated ALT levels >2 ULN should be considered for treatment. (Grade III).

3. HBeAg-negative patients:
 * HBeAg-negative patients with normal ALT and HBV DNA <2,000 IU/mL should be tested for ALT every 3 months during the ﬁrst year to verify that they are truly in the "inactive carrier state" and then every 6-12 months. (Grade III)
 * Tests for HBV DNA and more frequent monitoring should be performed if ALT or AST increases above the normal limit. (Grade III)