Hepatitis A Virus - HAV

Hepatitis A virus (HAV) is the most common cause of viral hepatitis worldwide. However, the targeted use of the HAV vaccine in the U.S. since 1995 has led to a 92% decrease in the number of reported cases. Testing for acute hepatitis by panel allows for identification of viral etiology.

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Diagnosis

Indications for Testing

  • New onset of jaundice, anorexia, dark urine, abdominal pain
  • Hepatomegaly, splenomegaly, bradycardia, lymphadenopathy, elevated transaminase levels
  • Suspected exposure to hepatitis A virus (HAV)

Laboratory Testing

  • HAV information for health professionals (CDC, 2015)
  • HAV case definition and classification (CDC, 2012)
  • Initial testing (nonspecific)
    • CBC – usually normal
    • Transaminases – usually markedly elevated
  • Testing for acute hepatitis
  • HAV IgM antibodies
    • Diagnose acute HAV infection if exposure is suspected or documented
    • Antibodies generally appear 4 weeks after infection (~5 days before symptoms)
    • May persist up to 6 months after onset of clinical symptoms
  • Total HAV antibodies (IgM and IgG)
    • Assess immunity for HAV from vaccination or previous infection (presence of antibodies is associated with immunity)
    • IgG does not appear until convalescent phase but remains detectable for life
    • Refer to Immunization Status topic for more information

Differential Diagnosis

Background

Epidemiology

  • Incidence – 1/100,000
    • Most common cause of viral hepatitis worldwide
    • 2,000 cases in the U.S. in 2009 (CDC)
    • 50-70% of U.S. adults have antibodies
  • Age – more prevalent among daycare and school-aged children
  • Transmission
    • Fecal-oral (unlike hepatitis B [HBV] or hepatitis C [HCV])
    • Ingestion of contaminated food or water
    • Occurs sporadically or in epidemics
    • Virus only viable on fomites, including produce, for about 1 week
    • Viral shedding in the stool lasts up to 6 months, but period of greatest contagiousness is the 2 weeks prior to onset of jaundice

Organism

  • Nonenveloped RNA picornavirus
  • Infects only primates
  • Survives for extended periods in seawater, fresh water, waste water, and soil
  • Resistant to freezing, detergents, and acids
  • Resistant to bile lysis due to lack of lipid envelope
  • Infects hepatocytes – no propensity for chronic infection

Risk Factors

  • Raw seafood
  • Infected food handlers
  • Daycare settings
  • International travel – accounts for ~50% of cases
  • No specific risk factors found in 70% of U.S. patients

Clinical Presentation

  • Usually asymptomatic or with mild symptoms after incubation period of ~28 days
  • Symptoms include fever, nausea, malaise, jaundice, dark urine, abdominal pain, anorexia
  • Symptoms last an average of 2 months
  • Signs include hepatomegaly, splenomegaly, bradycardia, lymphadenopathy, elevated transaminase levels
  • No chronic hepatitis sequelae
  • Complications – range from asymptomatic to acute, debilitating disease
  • Case fatality rate for HAV infection
    • 0.3-0.6% overall
    • As high as 1.8% among persons >50 years
  • May be prolonged with HIV coinfection
  • Significant liver disease is more likely to result in patients with coinfection of HBV or HCV or in pregnant women

Prevention

  • Universal vaccination against HAV recommended for
    • Children 1-18 years
    • High-risk groups, including men who have sex with men, drug abusers, and people who frequently travel to countries endemic for the virus
  • Strong immunity results even from relatively low vaccination rates
  • Vaccination is recommended prior to school entry or travel to endemic areas
  • After vaccination, immunity is active within ~1 week and therefore vaccination is useful as postexposure prophylaxis if given within 2 weeks of exposure
  • Vaccination is useful in event of community outbreak
  • Intramuscular IgG from pooled human plasma after exposure provides passive protection for ~6 months

ARUP Lab Tests

Evaluate viral etiology in patients with acute hepatitis

Not recommended for screening asymptomatic patients

Panel includes HAV IgM, HBV core antibody IgM, HBV surface antigen, HCV antibody

Reflex pattern: if results for HBsAg are repeatedly reactive with an index value between 1.00 and 50.00, then HBsAg confirmation testing will be added

Diagnose acute HAV infection if exposure suspected or documented

For panel test that includes HAV IgM, HBV core antibody IgM, HBV surface antigen, and HCV antibody, refer to acute hepatitis panel with reflex to HBV confirmation

May be helpful when assessing immunity

Not generally recommended to diagnose acute infection

Assay detects both IgG and IgM antibodies but does not differentiate between them

Initial screening for hepatobiliary inflammation

Panel includes albumin; alkaline phosphatase (ALP); aspartate aminotransferase (AST); alanine aminotransferase (ALT); bilirubin, direct; protein, total; and bilirubin, total

Related Tests

Identify infectious processes

Panel is not recommended

Order hepatitis A virus IgM antibody to diagnose acute infection

Order HAV total for assessing immunity

Medical Experts

Contributor

Genzen

Jonathan R. Genzen, MD, PhD
Associate Professor of Clinical Pathology, University of Utah
Chief Operations Officer, Medical Director of Automated Core Laboratory and Farmington Health Center Clinical Laboratory, ARUP Laboratories
Contributor

Lehman

Christopher M. Lehman, MD
Associate Professor of Clinical Pathology, University of Utah
Medical Director, University of Utah Health Hospital Clinical Laboratory, ARUP Laboratories
Contributor

Slev

Patricia R. Slev, PhD
Associate Professor of Clinical Pathology, University of Utah
Section Chief, Immunology; Medical Director, Immunology Core Laboratory, ARUP Laboratories

References

Additional Resources