Hepatitis A laboratory findings
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Hepatitis A cannot be differentiated from other types of viral hepatitis on the basis of clinical or epidemiologic features alone. Laboratory tests are required for its diagnosis. Serologic tests in hepatitis A virus (HAV) infection reveal elevated IgM anti-HAV in the acute phase (gold standard) in addition to an elevated IgG anti-HAV that remains elevated for the person's lifetime. Additional laboratory findings include the detection and sequencing of HAV RNA, an elevated direct bilirubin, and elevated liver enzymes. Liver biopsy has a minimal role in the diagnosis of HAV infection and it is only used when the diagnosis is unclear or when relapse is suspected.
- Is the gold standard for the detection of acute illness.
- Becomes detectable 5-10 days before the onset of symptoms and can persist for up to 6 months after infection
- Does not always indicate acute infection in asymptomatic adults. IgM anti-HAV can be present in the following cases:
- Appears early in the course of infection
- Remains detectable for the person's lifetime, conferring protection against reinfection
- Confers lifelong protection against the disease
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.
- HAV RNA can be detected in the blood and stools of the majority of persons during the acute phase of infection by using nucleic acid amplification methods.
- 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, which makes them not commonly used in the diagnosis of HAV infection.
Liver Function Tests
- 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
- Acute phase reactants, such as CRP and erythrocyte sedimentation rate (ESR), are commonly elevated in hepatitis A.
- Bower WA, Nainan OV, Margolis HS. Duration of viremia in naturally-acquired hepatitis A viral infections. [Abstract 103] In: Abstracts of the Infectious Diseases Society of America 35th Annual Meeting. Alexandria, VA: Infectious Diseases Society of America, 1997.
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- Hutin YJ, Pool V, Cramer EH, Nainan OV, Weth J, Williams IT, Goldstein ST, Gensheimer KF, Bell BP, Shapiro CN, Alter MJ, Margolis HS (1999). "A multistate, foodborne outbreak of hepatitis A. National Hepatitis A Investigation Team". The New England Journal of Medicine. 340 (8): 595–602. doi:10.1056/NEJM199902253400802. PMID 10029643. Retrieved 2012-02-28. Unknown parameter
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