Hepatitis A laboratory findings

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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]

Laboratory Findings

Hepatitis A cannot be differentiated from other types of viral hepatitis on the basis of clinical or epidemiologic features alone.

Serologic Tests

Serologic testing to detect immunoglobulin M (IgM) antibody to the capsid proteins of HAV (IgM anti-HAV) is required to confirm the diagnosis of acute HAV infection.

• Immunoglobulin M (IgM) anti-HAV:

• Required to confirm the diagnosis of acute HAV infection
• In most persons, it becomes detectable 5-10 days before the onset of symptoms and can persist for up to 6 months after infection

• Immunoglobulin G (IgG) anti-HAV:

• Appears early in the course of infection
• Remains detectable for the person's lifetime
• Confers lifelong protection against the disease

Two serologic tests are licensed for the detection of antibodies to HAV:

• IgM anti-HAV
• Total anti-HAV (IgM and IgG anti-HAV)

In the majority of patients, IgM anti-HAV declines to undetectable levels less than 6 months after infection. However, persons who test positive for IgM anti-HAV, more than 1 year after infection have been reported, as have likely false-positive tests in persons without evidence of recent HAV infection.

Total anti-HAV testing is used in epidemiologic studies to measure the prevalence of previous infection or by clinicians to determine whether a person with an indication for pre-exposure prophylaxis is already immune.

Sensitive tests for immunoglobulin M (IgM) and immunoglobulin G (IgG) anti-HAV in saliva have been developed but are not licensed in the United States.

Serum IgG, IgM and ALT following Hepatitis A virus infection

• HAV RNA can be detected in the blood and stool of the majority of persons during the acute phase of infection by using nucleic acid amplification methods, and nucleic acid sequencing has been used to determine the relatedness of HAV isolates for epidemiologic investigations. However, only a limited number of research laboratories have the capacity to use these methods.

• HAV RNA can be detected in the blood and stool of most persons during the acute phase of infection by using nucleic acid amplification methods, and nucleic acid sequencing has been used to determine the relatedness of HAV isolates. However, these methods, available in only a limited number of research laboratories, generally are not used for diagnostic purposes.

Liver Function Tests

Liver enzymes such as aminotransferase and alkaline phosphatase are elevated with high levels of serum total and direct bilirubin among patients with Hepatitis A. The serum levels of alanine aminotransferase (ALT) are usually higher than aspartate aminotransferase (AST). Bilirubin levels tends to increase after the elevation of serum aminotransferase.

Other Laboratory Findings

• Elevated erythrocyte sedimentation rate (ESR)
• Acute phase reactants
• Immunoglobulins are the other lab findings that may be evident in patients infected with Hepatitis A.

Liver Biopsy

The role of a liver biopsy is minimal in the diagnosis of hepatitis A. It may be used in cases involving chronic relapsing hepatitis A or when the diagnosis is unclear.