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- [Voiceover] Hepatitis C liver disease,
caused by the hepatitis C virus,
referred to as HCV,
can be acute or chronic.
Although most persons, 70-85%,
with newly acquired HCV infection are asymptomatic,
most, up to 85%, will go on to have chronic infection.
Those who clear the virus on their own
are said to have resolved infection.
Since antiviral treatment is intended for persons
with current HCV infection,
it is important to distinguish people with chronic infection
from those whose infection has resolved.
In recently acquired HCV infection,
liver enzymes may be elevated to 200IU/L or more.
This is depicted here
by the enzyme alanine aminotransferase, ALT, shown in blue.
Since most newly infected persons
have no symptoms of hepatitis,
they are often not identified and diagnosed
with acute hepatitis C.
If symptoms do occur, as depicted by the purple bar,
it is usually six to seven weeks after exposure,
ranging from two to 26 weeks,
and they persist during the time
when enzyme levels are elevated.
About 40% of persons infected
will have detectable antibody to HCV,
called anti-HCV and represented by the solid pink line,
in serum approximately 10-11 weeks after exposure,
with the percent increasing to 80% by 15 weeks,
and virtually all infected persons
will present the antibodies
by six months following exposure.
When following up someone with a known exposure to HCV,
this is important to keep in mind.
Anti-HCV remains positive generally for life.
HCV ribonucleic acid, HCV RNA, a marker for viremia,
can be detected in the blood with a nucleic acid test,
also known as a NAT assay,
as early as one to two weeks after exposure.
In patients with recently acquired HCV infection
who resolve their infection,
liver enzyme levels return to normal
and HCV RNA disappears as anti-HCV rises.
Antibody tests alone,
either rapid or laboratory-conducted assays,
cannot distinguish between a recently acquired,
chronic, or resolved infection.
Chronic infection is characterized
by the persistent presence of HCV RNA, shown in yellow,
and may be accompanied by fluctuating ALT levels,
shown in blue, indicating continuing liver inflammation.
ALT levels seen in patients with chronic HCV infection
are elevated, but tend to be lower
than patients with recently acquired HCV infection.
In fact, ALTs can be intermittently normal
in patients with chronic infection
Here is the recommended testing sequence
for identifying current HCV infection:
If the HCV antibody, anti-HCV, test result is nonreactive,
there is no detectable antibody to HCV,
and, unless there are special circumstances,
such as recently exposed, immuno-compromised,
or other special medical circumstances,
the person can be considered never infected
and therefore susceptible.
If anti-HCV is reactive,
this indicates either current HCV infection,
past HCV infection that has resolved,
or false positive test result.
A reactive anti-HCV test result
should be followed by a NAT for HCV RNA.
If HCV RNA is detected,
this indicates current HCV infection.
If HCV RNA is not detected,
this indicates either past HCV infection that has resolved,
or a false positive anti-HCV test result.
As with a nonreactive anti-HCV test result,
a person with a negative HCV RNA test
who has a known or expected exposure to HCV
within the prior six months,
or with other medical issues that may impact test results,
should be followed up as recommended elsewhere.
(electronic music) This segment is now complete.