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Explanation of Viral Hepatitis Tests

Test

Interpretation of Results and Comments

IgM Antibody to Hepatitis A

(Anti-HAV IgM or HAV IgM Ab)

  • Positive result defines a recent HAV infection.
  • May be negative in early infection (if collected within 5 to 7 days after onset of symptoms).
  • Present for 3 to 6 months after onset of acute infection.

IgG Antibody to Hepatitis A

(Anti-HAV Ab or HAV Ab)

  • Of extremely limited value in the diagnosis of acute infection.
  • Positive result indicates past infection and immunity to HAV.
  • Individuals given serum immune globulin for HAV prophylaxis may test as positive for at least six months.

Hepatitis B Surface Antigen

(HBsAg)

  • Used to diagnose an acute or chronic infection.
  • First marker to appear in an acute infection.
  • Disappearance indicates recovery from infection.
  • Persistence for > 6 months indicates chronic infection (carrier).
  • Individuals tested within 72 hours after administration of the vaccine may test as positive. (See anti-HBs, anti-HBc IgM and HBeAg)

Antibody to Hepatitis B Surface Antigen

(Anti-HBs or HBs Ab)

  • Only test which can be used to assess presence of protective immunity after immunization with hepatitis B vaccine.
  • Routine monitoring of levels in individuals who have received the complete course of vaccine is not considered necessary.
  • Some individuals, e.g. healthcare workers, who are believed to have been exposed to the virus by a needlestick injury, should have their anti-HBs levels tested to determine whether they require administration of hepatitis B immune globulin (HBIG) and hepatitis B vaccine booster.
  • Positive result in individuals with recent acute HBV infection indicates convalescence.
  • Usually NOT detected when HBsAg is also present.
  • In some cases of chronic hepatitis B infection, both HBsAg and anti-HBs can be detected.  These antibodies are heterotypic and likely not protective.
  • Antibody levels may decline with time.

IgM Antibody to Hepatitis B Core Antigen

(Anti-HBc IgM or HBc IgM Ab)

  • This test is expensive and should primarily be used if there is a high index of suspicion to indicate that the patient is in the early convalescence “window period” (2 to 16 weeks post infection) when HBsAg has disappeared and anti-HBs levels are not yet detectable.
  • Positive result in patients who are also HBsAg positive usually indicates acute infection.
  • Usually detectable for 3 to 12 months.
  • Depending upon the threshold level of sensitivity, low levels may be detected in patients with chronic infection and reactivation.

Hepatitis Be Antigen

(HBeAg)

  • Marker of active HBV replication.
  • Also a marker of infectivity. However, the absence of HBeAg in a person who is HBsAg-positive does not imply that the individual is NOT infectious.
  • Can be used to monitor therapy of patients with chronic HBV infection.

Antibody to Hepatitis Be Antigen

(Anti-HBe or HBe Ab)

  • Appears as HBeAg disappears.
  • In chronic hepatitis B infection, a positive result indicates resolving or minimal liver disease.
  • However, individuals who are HBsAg-positive and have anti-HBe present must still be considered infectious.

Total Antibody to Hepatitis B Core Antigen

(Anti-HBc or HBc Ab)

  • A positive result indicates past infection with hepatitis B virus.
  • Usually persists for life.
  • This antibody is absent in individuals who are immune solely as a result of vaccination.
  • Up to 10% false-positive rate has been described in individuals with no documented infection to HBV.  If uncertain, presence of one other marker, e.g., anti-HBs or anti-HBe would confirm previous exposure with HBV.  Alternatively a negative repeat test later may indicate an earlier false-positive result.

Hepatitis B viral DNA

(HBV DNA)

  • Of very limited value in the diagnosis of HBV infection.
  • Used to determine the presence of HBV DNA circulating in the blood which is a measure of virus replication in the liver.
  • Primary use is in monitoring treatment and clarifying some complex situations.

Antibody to Hepatitis C

(Anti-HCV or HCV Ab)

  • Enzyme immunoassay (EIA) tests are the most common screening tests used to detect antibody.
  • With present EIA tests, a reactive result may be obtained after 8 to 12 weeks to several months following infection with HCV.  Earlier generations of EIA tests often gave negative antibody results for up to 1 year.
  • False-positive results are found in patients with autoimmune chronic active hepatitis, alcoholic liver disease and other disorders relating to hypergammaglobulinemia.
  • Presence of antibody can be due to acute or chronic infection.  It may represent only evidence of an infection with HCV.
  • Persistently elevated ALT levels suggest chronic infection.  Repeatedly normal levels do not exclude chronic infection, but suggest low grade inflammation.
  • ALT values in some patients with HCV infection are within normal ranges.

Polymerase Chain Reaction for Hepatitis C

(PCR for HCV)

  • Used to determine the presence of HCV RNA circulation in the blood which is a measure of virus replication in the liver.
  • Can be used to assess the infectivity of the patient and monitor therapy.
  • May be of use in early infection when antibody to the virus is undetectable, and in immunocompromised patients who may not seroconvert.

Antibody to Hepatitis D virus

(Anti-HDV or HBV Ab)

  • HDV occurs as a co-infection with HBV or super-infection of a chronic HBsAg carrier.
  • Antibodies appear late during the course of acute infection.
  • HDV is uncommon in Canada.

Antibody to Hepatitis E virus

(Anti-HEV or HEV Ab)

  • Routine tests not presently available for detection of this agent.

ALT

alanine aminotransferase

  • Liver enzyme test.
  • Used to assess extent of liver inflammation and injury.
  • Can be used to monitor resolution of inflammation following acute or chronic infection.