Hepatitis B laboratory tests

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

Diagnosis of hepatitis is made by biochemical assessment of liver function. Initial laboratory evaluation usually reveals: total and direct bilirubin, ALT, AST, alkaline phosphatase, prothrombin time, total protein,albumin, globulin, complete blood count, and coagulation studies.

Laboratory Findings

Diagnosis of hepatitis is made by biochemical assessment of liver function. Initial laboratory evaluation should include:

• Total and direct bilirubin increased

• Severe disease is often associated with persistent bilirubin levels >340 mol/L

• ALT and AST increased
• Alkaline phosphatase - normal or mildly elevated
• Prothrombin time - Prolonged from synthetic defect, caused by hepatocellular necrosis
• Total protein - decreased
• Albumin
• Globulin - mildly elevated
• Complete blood count

• Initial lymphopenia and neutropenia, followed by relative lymphocytosis
• Anemia

Diagnosis is confirmed by demonstration in sera of specific antigens and/or antibodies. Three clinical useful antigen-antibody systems have been identified for hepatitis B:

• Hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs)
• Antibody (anti-HBc IgM and anti-HBc IgG) to hepatitis B core antigen (HBcAg)
• Hepatitis B e antigen (HBeAg) and antibody to HBeAg (anti-HBe)

Antigens	Description
HBsAg	Hepatitis B surface antigen is the earliest indicator of acute infection and is also indicative of chronic infection if its presence persists for more than 6 months. It is useful for the diagnosis of HBV infection and for screening of blood. Its specific antibody is anti-HBs. HBsAg indicates that the person is potentially infectious.
HBcAg	Hepatitis B core antigen is derived from the protein envelope that encloses the viral DNA, and it is not detectable in the bloodstream. When HBcAg peptides are expressed on the surface of hepatocytes, they induce an immune response that is crucial for killing infected cells. The HBcAg is a marker of the infectious viral material and it is the most accurate index of viral replication. Its specific antibody is anti-HBc.
HBeAg	Hepatitis B e antigen appearing during weeks 3 to 6 indicates an acute active infection at its most infectious period, and means that the patient is infectious. Persistence of this virological marker beyond 10 weeks shows progression to chronic infection and infectiousness. Continuous presence of anti-HBe indicates chronic or chronic active liver disease. HBeAg is not incorporated into virions, but is instead secreted into the serum. Mutant strains of HBV exist that replicate without producing HBeAg. HBeAg’s function is uncertain. Its specific antibody is anti-HBe.
HBxAg	Hepatitis B x antigen is detected in HBeAg positive blood in patients with both acute and chronic hepatitis. HBxAg is a transcriptional activator. It does not bind to DNA. Its specific antibody is anti-HBx.
HBV DNA	HBV DNA is detectable by PCR as soon as 1 week after initial infection, but the test is generally only performed for research purposes or to detect mutants that escape detection by current methods.
HBV DNA Polymerase	Tests for the presence of HBV DNA polymerase, detectable within 1 week of initial infection, are only performed for research purposes.

Antibodies	Description
Anti-HBs	This is the specific antibody to hepatitis B surface antigen. Its appearance 1 to 4 months after onset of symptoms indicates clinical recovery and subsequent immunity to HBV. Anti-HBs can neutralize HBV and provide protection against HBV infection.
Anti-HBc	This is the specific antibody to hepatitis B core antigen. Antibodies to HBc are of class IgM and IgG. They do not neutralize the virus. The presence of IgM identifies an early acute infection. In the absence of HBsAg and anti-HBs, it shows recent infection. IgG with no IgM may be present in chronic and resolved infections. Anti-HBc testing identifies all previously infected persons, including HBV carriers, but does not differentiate carriers and non-carriers.
Anti-HBe	This is the specific antibody to hepatitis B e antigen. During the acute stage of infection the seroconversion from e antigen to e antibody is prognostic for resolution of infection. Its presence in the patient’s blood along with anti-HBc and in the absence of HBsAg and anti-HBs indicates low contagiousness and convalescence.
Anti-HBx	This is the specific antibody to hepatitis B x antigen. It appears when other virological markers are becoming undetectable.

Serological Markers

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

Serological markers may vary throughout the course of the disease:

• Pre-S1 and pre-S2 antigens are present early in the incubation period. They are never detected in the absence of HBsAg.

• Hepatitis B virions, HBV DNA, DNA polymerase, and HBeAg are then also detected.

• The presence of HBeAg is associated with relatively high infectivity and severity of disease.

• Anti-HBc is the first antibody to appear. Demonstration of anti-HBc in serum indicates HBV infection, current or past.

• IgM anti-HBc is present in high titre during acute infection and usually disappears within 6 months, although it can persist in some cases of chronic hepatitis. This test may therefore reliably diagnose acute HBV infection.
• IgG anti-HBc generally remains detectable for a lifetime.

• Anti-HBe appears after anti-HBc and its presence correlates to a decreased infectivity. Anti-HBe replaces HBeAg in the resolution of the disease.

• Anti-HBs replaces HBsAg as the acute HBV infection is resolving. Anti-HBs generally persists for a lifetime in over 80% of patients and indicates immunity. Acute hepatitis patients who maintain a constant serum HBsAg concentration, or whose serum HBeAg persists 8 to 10 weeks after symptoms have resolved, are likely to become carriers and at risk of developing chronic liver disease.

Diagnostic Studies

The following studies are used to examine pathological specimens for the presence of HBV-associated antigens or particles. They provide information about the relationship between HBV DNA replication and HBV gene expression:

• Immunofluorescence studies
• In situ hybridization
• Immunohistochemistry
• Thin-section electron microscopy

PCR

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.

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

Class I

"1. HBeAg-positive and HBeAg-negative patients who meet criteria for chronic hepatitis B should be evaluated for treatment."

Class III

"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. 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. 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."

Class 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. Tests for HBV DNA and more frequent monitoring should be performed if ALT or AST increases above the normal limit."