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- [Voiceover] Liver disease caused by the hepatitis B virus,
referred to as HBV,
can be either acute or chronic.
The first serologic marker to appear in someone infected
following exposure to HBV,
is hepatitis B surface antigen,
referred to as HBsAg.
HBsAg, shown by the red hatched line,
can be detected on average,
one month after exposure to the virus,
but can range from as early as one week
to nine weeks after exposure,
and may precede the onset of symptoms
by one to two months.
Symptoms, when present, occur on average
twelve weeks after exposure to HBV,
with a range of nine to 21 weeks.
This period is noted by the green bar.
When the serologic test for HBsAg is positive,
HBV DNA can usually be detected in the patient’s blood.
The duration of detection of HBsAg,
and hence HBV DNA, is variable.
About 50% of patients will test negative
for HBsAg and HBV DNA by seven weeks
after symptoms of acute illness have appeared.
All patients who recover from an acute infection
will be HBsAg and HBV DNA negative
by 15 weeks after the appearance of symptoms.
Hepatitis B e-antigen, referred to as HBeAg,
is usually detectable in patients with acute disease,
and is noted by the green bar.
The presence of HBeAg in serum
generally correlates with higher titers of virus
and greater infectivity,
while the presence of antibody to hepatitis B e-Antigen,
referred to as anti-HBe,
shown by the yellow bar,
denotes lower levels of virus and thus, less infectivity.
A diagnosis of acute hepatitis B
can be made on the basis of detection of IgM class antibody
to hepatitis B core antigen,
IgM anti-HBc.
This serologic marker is depicted by the pink hatched line.
IgM anti-HBc is usually detectable
at the onset of symptoms,
and becomes undetectable within six to nine months.
Total antibody, IgM and IgG,
to hepatitis B core antigen,
referred to as total anti-HBc,
and illustrated by the purple hatched line,
persists indefinitely as a marker of past infection.
Antibody to hepatitis B surface antigen,
referred to as anti-HBs,
is depicted by the orange hatched line.
Anti-HBs becomes detectable during convalescence
and after the disappearance of HBsAg,
and generally indicates recovery
and immunity from reinfection.
There is a period of time,
often called the window period,
which occurs after the disappearance of HBsAg
and before the appearance of anti-HBs.
During this window period,
when using routine tests for diagnosis of acute hepatitis,
IgM anti-HBc
and total anti-HBc,
may be the only serologic markers present.
There is also a period of time soon after exposure
when these routine tests will find
only the hepatitis marker HBsAg, present.
A person with chronic hepatitis B virus infection,
will have both hepatitis B surface antigen,
HBsAg shown in red,
and total antibody to hepatitis B core antigen,
total anti-HBc shown in blue,
persistently detectable by serologic testing
throughout the duration of chronicity.
HBV DNA will usually be detectable in serum as well,
using a nucleic acid test, or NAT.
Hepatitis B e-antigen,
HBeAg shown in green,
generally indicates higher levels of HBV DNA,
and thus greater infectivity.
Presence of antibody to hepatitis B e-antigen,
anti-HBe shown in purple,
conveys just the opposite scenario.
Chronic HBV infection is diagnosed
when a patient has a positive serologic test result
for either HBsAg
or HBeAg
or HBV DNA
on at least two separate samples,
six months apart.
Or when a patient has a positive test
for any one of these on a single sample,
and has a negative test for IgM anti-HBc.
Successful vaccination against HBV infection
results in production of anti-HBs,
with sero-protection defined as an anti-HBs level
of 10 milli-International Units per milliliter or more
one to two months after completion
of the vaccination series.
HBsAg may be transiently positive
for two to three weeks after vaccination,
but this is clinically insignificant.
A serologic test result of anti-HBs positive alone
indicates immunity following vaccination
with at least three doses of hepatitis B vaccine.
Without repeated exposure to HBV,
antibody levels will naturally decline over time.
But immunity is likely maintained
even if levels decline below 10 mIU/mL.
This table summarizes the interpretation
of serologic test results for HBV infection.
Negative results for hepatitis B surface antigen,
HBsAg,
total antibody to hepatitis B core antigen,
total anti-HBc,
immunoglobulin M, IgM, anti-HBc,
and antibody to hepatitis B surface antigen,
anti-HBs,
should be interpreted as never infected,
and therefore susceptible.
Positive HBsAg,
with the other 3 tests being negative,
indicates early acute infection,
but could also indicate receipt of the vaccine
within several weeks.
This is a transient effect.
Positive HBsAg,
total anti-HBc,
and IgM anti-HBc,
with negative anti-HBs indicates acute infection.
As acute infection resolves,
HBsAg will disappear,
and before anti-HBs appears,
both HBsAg and anti-HBs will be negative,
while total anti-HBc
and IgM anti-HBc will be positive.
Negative HBsAg and IgM anti-HBc,
with positive total anti-HBc and anti-HBs,
indicates past infection with recovery
and immunity to new infection.
Positive HBsAg and total anti-HBc,
with IgM anti-HBc and anti-HBs negative
indicates chronic infection.
Total anti-HBc positive alone,
with the other 3 negative,
has several possible interpretations,
including a false positive result
and therefore susceptible.
Past infection resolved.
Low-level chronic infection,
and unlikely to be infectious
except under unusual circumstances
involving direct percutaneous exposure
to large quantities of blood,
such as blood transfusion,
or passive transfer of anti-HBc
to an infant from an infected mother.
Anti-HBs alone
should be detected following vaccination,
as described previously,
or may be detected for 3-6 months
following receipt of Hepatitis B Immune Globulin,
H-BIG,
also commonly referred to as H-Big.
This segment is now complete.
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