Get The Facts About Hepatitis C Viral Load
Upon being diagnosed with Hepatitis C, the myriad of subsequent tests can seem like a flurry of being poked and prodded. As one of the primary markers physicians use to assess this illness, viral load’s significance can be misleading. One of the most common misconceptions among Hepatitis C patients is that a higher viral load indicates a greater severity of their disease. This causes many people to incorrectly conclude that if their viral load is high they are in much more serious trouble than if it was low. However, the primary purpose of viral load testing is to determine someone’s candidacy, progress and success for Hepatitis C antiviral treatment.
Hepatitis C is a viral infection of the liver. However, the virus does make its way outside of the liver. This is why Hepatitis C can be measured in the bloodstream. A viral load test determines how many viral particles are floating around in the blood. These particles contain RNA, copies of Hepatitis C’s genetic material. There are three types of tests used to evaluate viral load:
- PCR (Polymerase Chain Reaction) – PCR tests measure Hepatitis C RNA in the blood to tell if there is an active infection. This test can measure small amounts of the virus (5-10 IU/mL).
- bDNA (Branched-chain DNA) – The bDNA test only measures medium to high viral loads above 50 IU/mL. This means that if a person has a viral load below 50 IU/mL, a bDNA test may not be able to detect the virus.
- TMA (Transcription-mediated amplification) – The TMA test also measures Hepatitis C RNA in a blood sample. The TMA test can measure very small amounts of the virus (as few as 5-10 IU/mL).
Results of these viral load tests can be translated in two ways – either in the number of copies of the virus per milliliter or by International Units per milliliter (IU/mL). Physicians often differ in their opinion about what constitutes a high or a low viral load measurement. While these ranges may not be completely agreed on, the following measurements generally denote a high or low Hepatitis C viral load:
When expressed in terms of copies per mL:
- Low = fewer than 2 million copies
- High = greater than 2 million copies
When expressed in terms of International Units per mL:
- Low = fewer than 800,000 IU/mL
- High = greater than 800,000 IU/mL
Viral load does not appear to correlate with a person’s wellness. In fact, a person with a viral load below 200,000 (in terms of copies/mL) may not be able to get out of bed because of their Hepatitis C infection – while someone with a viral load of 10 million (in terms of copies/mL) could feel fine. When it comes to determining liver disease severity, a liver biopsy – or similarly equivalent method – is the only way for a physician to accurately determine his or her patient’s health. This is because a liver biopsy – not viral load – physically examines liver tissue to see how much damage actually exists.
Although Hepatitis C viral load is not a measure of liver disease severity, it is an important marker for several other reasons:
- A viral load test can determine if the Hepatitis C virus is still present in the body, or if it has been cleared.
- The chance of a pregnant woman passing the virus on to her child is very low – unless she has a high viral load. An expectant mother with a high viral load has a slightly greater chance of passing the virus to her baby.
- Numerous studies have shown that people with lower Hepatitis C viral loads respond better to interferon therapy than those with higher viral loads. This information may help physicians determine who is a good candidate for interferon therapy.
- For those on interferon treatment, viral load testing helps physicians determine if the treatment is working and how long a person should take it.
When a physician evaluates your viral load to see if you are responding to interferon treatment, they look at this number in terms of logarithims:
- A 1-log change is a 10-fold difference.
- Significant changes in viral load are a 2-log difference or a 100-fold change. Differentiating between a 1- and 2-log change can be deceiving.
- A viral load of 800,000 that drops down to 400,000 might appear to be a big drop but it’s only changed by a factor of two – which is just a fraction of a 1-log change.
- However, a change from 800,000 to 8,000 would be significant – as that is a 100-fold change.
- In general, if a person’s viral load has dropped 2 logs or more after 12 weeks of antiviral treatment, there is a greater chance that his or her treatment will be successful.
Besides viral load’s use for monitoring during treatment, it is also used to evaluate the success of Hepatitis C treatment. Viral load is measured to see if the person achieved a sustained virilogic response (SVR). Achieving SVR means that six months after antiviral treatment was completed, viral load tests found no detectable Hepatitis C virus in the blood.
Hepatitis C viral load will normally fluctuate throughout the course of anyone’s illness. In and of itself, viral load is not a reason for concern. It may sound like a good measure of how someone is faring with Hepatitis C. But outside of this test’s use to determine if someone is a candidate for treatment, to monitor treatment or to see if treatment was successful, Hepatitis C viral load reveals very little about the degree of a person’s liver disease.
http://www.ehow.com/how_4448469_understand-hepatitis-c-viral-load.html, How to Understand Hepatitis C Viral Load, Richard Ferri, Retrieved December 3, 2009, eHow, Inc., 2009.
http://www.hcvadvocate.org/hepatitis/Basics/Viralload_09.pdf, HCV Viral Load Tests, Alan Franciscus, Retrieved December 3, 2009, The Hepatitis C Support Project, 2009.