Hepatitis B laboratory tests

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:

Antigens	Antibodies
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 with this virus; 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 serologic 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; however, some variants of the hepatitis B virus do not produce the 'e' antigen at all, 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 afterward. 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 antibodies to the hepatitis B surface antigen (anti-HBs).

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.

Hepatitis B viral antigens and antibodies detectable in the blood following acute infection.

Hepatitis B viral antigens and antibodies detectable in the blood of a chronically infected person

Diagnostic Criteria

Stage of Hepatitis B	Lab Findings
Chronic State	1. HBsAg-positive >6 months
	2. Serum HBV DNA >20,000 IU/mL (105copies/mL), lower values 2,000- 20,000 IU/mL (104-105copies/mL) are often seen in HBeAg-negative chronic hepatitis B
	3. Persistent or intermittent elevation in ALT/AST levels
	4. Liver biopsy showing chronic hepatitis with moderate or severe necroinflammation
Carrier State	1. HBsAg-positive >6 months
	2. HBeAg–, anti-HBe+
	3. Serum HBV DNA <2,000 IU/mL
	4. Persistently normal ALT/AST levels
	5. Liver biopsy confirms absence of significant hepatitis
Resolved	1. Previous known history of acute or chronic hepatitis B or the presence of anti-HBc ± anti-HBs
	2. HBsAg-
	3. Undetectable serum HBV DNA
	4. Normal ALT levels

Recommendations for Monitoring Patients with Chronic HBV Infection: AASLD Practice Guidelines 2009

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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)

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References