Hepatitis A Virus - HAV

Diagnosis

Indications for Testing

  • New onset of jaundice, anorexia, dark urine
  • Known exposure to hepatitis A virus (HAV)

Laboratory Testing

  • Hepatitis A information for health professionals (CDC)
  • 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) indicate past infection or immunization – presence associated with immunity
    • Assess immunity for HAV from vaccination or previous infection
    • IgG does not appear until convalescent phase but remains detectable for life

Differential Diagnosis

Clinical Background

The targeted use of the hepatitis A (HAV) vaccine in the U.S. since 1995 has led to a 92% decrease in the number of reported cases of HAV.

Epidemiology

  • Incidence
    • Most common cause of viral hepatitis worldwide
    • Incidence – 1/100,000
      • 2,000 cases in the U.S. in 2009 (CDC)
    • 50-70% of U.S. adults have antibodies
  • Age – more prevalent among day-care and school-aged children
  • Transmission
    • Fecal-oral (unlike hepatitis B or C)
    • 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 the period of contagiousness highest during the two weeks prior to onset of jaundice

Organism

  • Nonenveloped RNA picornavirus
  • Infects only primates
  • Virus survives for extended periods in seawater, fresh water, waste water, and soil
  • Resistant to freezing, detergents, and acids
  • Lack of lipid envelope confers resistance to bile lysis
  • Virus infects the hepatocytes – no propensity for chronic infection

Risk Factors

  • In the U.S., 70% of patients have no specific risk factors
  • Raw seafood
  • Infected food handlers
  • Day-care settings
  • International travel – accounts for ~50% of cases

Clinical Presentation

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

Treatment

  • Supportive

Prevention

  • Universal vaccination against HAV recommended for the following
    • 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 prior to school entry or travel to endemic areas
    • After vaccination, immunity is active within ~1 week and therefore useful as post-exposure prophylaxis if given within 2 weeks of exposure
      • Useful in community outbreak
  • Intramuscular IgG from pooled human plasma after exposure provides passive protection for ~6 months

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Hepatic Function Panel 0020416
Method: Quantitative Enzymatic/Quantitative Spectrophotometry

Initial screening for hepatobiliary inflammation

Panel includes albumin; ALP; AST; ALT; bilirubin, direct; protein, total; and bilirubin, total

    
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Identify infectious processes

    
Hepatitis Panel, Acute with Reflex to HBsAg Confirmation 0020457
Method: Qualitative Chemiluminescent Immunoassay

Order to 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

    
Hepatitis A Virus Antibodies (Total) 0020591
Method: Qualitative Chemiluminescent Immunoassay

Order only when assessing immunity for HAV from either vaccination or previous infection

Do not use to diagnose acute infection

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

  
Hepatitis A Virus Antibody, IgM 0020093
Method: Qualitative Chemiluminescent Immunoassay

Order to diagnose acute HAV infection if exposure suspected or documented

High sensitivity and specificity when patients are symptomatic

 False-positive rates are high with more than 60% of positive HAV IgM antibody results reported on patients who do not meet clinical criteria  
Additional Tests Available
 
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Hepatitis A Virus Panel 0020597
Method: Qualitative Chemiluminescent Immunoassay

Panel not recommended to diagnose acute hepatitis A virus infection or for assessing immunity

Order hepatitis A virus IgM antibody to diagnose acute infection

Order HAV total for assessing immunity

Diagnostic Algorithm