Viral Load Information
- HEALTHY HEPPER NEWSLETTER 8/2/2008
Topic: Hepatitis C (HCV) and Viral Load Questions and Answers
What is HCV viral load? Why does it matter? If you're being treated
for hepatitis C virus (HCV) infection, your doctor is keeping track of
your viral load. WebMD got answers to your most frequently asked
questions from two experts:
a.. Frank Anania, MD, associate professor of medicine and director of
hepatology at Emory University School of Medicine in Atlanta.
b.. Brian L. Pearlman, MD, medical director of the center for
hepatitis C at the Atlanta Medical Center, Atlanta; and associate
professor, Medical College of Georgia in Augusta.
What is HCV viral load
Dr. Pearlman:Viral load is [the number of] viral particles floating in
the blood. These are copies of the genetic material of the virus
circulating though the body.
Dr. Anania: Viral load is based on technology that lets us measure
extremely small quantities of hepatitis C virus RNA, the building
block of the virus.
Can I be positive for hepatitis C if I don't have any measurable viral
Dr. Pearlman: Being "hepatitis C positive" means you have anti-HCV
antibodies in your blood. Having HCV antibodies just means you've been
exposed to the hepatitis C virus. You can certainly be antibody
positive and not have any measurable viral load. One lucky thing this
might mean is that you are one of the 15% to 40% of people who
naturally clear the virus from their bodies. The other possibility is
that the virus, during the time blood is drawn, was only temporarily
undetectable. HCV viral load in the blood goes up and down, and the
test might have caught it on a downswing. So before we tell someone
they are negative, we ask them to have the test repeated.
Dr. Anania: After hepatitis C treatment, people still have antibodies
to HCV. But if they have no detectable HCV viral load, that indicates
recovery from infection -- that is, response to treatment and
sustained remission. Over a period of time, if a later viral load test
comes back detectable, that patient is in remission.
What is a low viral load and what is a high viral load? What does this
Dr. Pearlman: Anything over 800,000 IU/mL is high. Anything under that
is low viral load.Those with low viral load have a better chance of
responding to treatment.
If my viral load is rising, am I getting sicker?
Dr. Anania: Not necessarily. With HCV, viral burden in hepatitis C
does not necessarily predict the natural history of clinical disease.
And therefore, patients need to understand that we use that
measurement to help us guide therapy and response to therapy. We use
it in conjunction with other types of laboratory data -- liver
enzymes, liver biopsies sometimes, and viral genotype. Taken all
together, these tests give us a snapshot of what is going on. But
viral load numbers do not predict disease.
Dr. Pearlman: Unlike HIV, HCV viral copies do not directly affect a
patient's prognosis and how fast disease is progressing in the liver.
Remember, we are measuring blood levels, not what is happening in
liver cells. HIV viral load does have a lot to do with quicker
progression to AIDS. But HCV viral load does not tell you how fast
hepatitis is progressing.
Does a drop in my HCV viral load mean my treatment is working?
Dr. Pearlman: We often talk about viral load numbers, but we really
look at this in terms of logarithms. A "1 log" change is a 10-fold
difference. Significant changes in viral load are a 2-log difference
or a 100-fold change. This can be deceptive. If you have a viral load
of 800,000 and it drops to 400,000, that seems like a big drop. But
it's only changed by a factor of two. A change from 800,000 to 8,000
would be significant. This is important when we look at response to
treatment. Twelve weeks after starting treatment, we see if a person's
viral load has dropped 2 logs or more from baseline. If it has not, we
are almost sure the treatment is not going to work.
How many months of no detectable viral load have to pass before I'm
Dr. Anania: Generally we like to see six months of continued
undetectable viral load after treatment to say a patient's virus is in
remission. I cannot say they are "cured."
Dr. Pearlman: The best we can tell patients in 2004 is that after
treatment, they have a "sustained virologic response" or SVR. That is
defined as undetectable viral load by PCR to under 50 IU/mL for 24
weeks after treatment is complete. If that is the case, that is an
SVR. SVR means it's 98% certain you are cured. But there are very rare
cases where people relapse if you check their viral load a year or two
out. But it doesn't mean you can't get hepatitis C again if you engage
in high-risk behaviors.
***Note: Being "cured" is possible. To see more on two individual
who pursued wholistic treatment for Hep C and were "cure" visit
Does the viral load respond differently to different brands of
hepatitis C treatments?
Dr. Pearlman: The two major pegylated interferon products for treating
hepatitis C -- Pegasys and Peg-Intron in combination with ribavirin --
in general show similar response rates. Slight variations may be
reported in different clinical trials with different subsets of patients.
What are the different ways of measuring HCV viral load?
Dr. Pearlman: RNA is the genetic material all these tests measure.
Most experts measure it by a technique called RNA polymerase chain
reaction or PCR. There's also a technique called branched chain DNA,
and a newer technique called transcription mediated amplification or
TMA. These are just different ways of measuring HCV RNA. TMA probably
gets down to detecting the fewest number of copies, but most labs use PCR.
HCV viral load used to be measured in number of copies. Now they use
international units. What gives?
Dr. Pearlman: Different laboratories don't use the same standard for
counting copies of HCV RNA. So we're now moving to an international
Dr. Anania: You can still get a copy number. But using international
units (IU) is a way to uniformly report data throughout the world.
Many lab tests are reported in this way. It standardizes test results
between different labs."
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