Hepatitis B Tests HBV DNA

Viral Load Testing - HBV DNA

This is the new area of testing for hepatitis B. It is still not a routine test for all clinics. It is the best indicator of how infectious someone with chronic hepatitis B is. Unfortunately, there have been many versions of this test over the years.

In the 1990s, we measured viral load with a test called Digene. You can imagine that viruses are very small and you need a lot of viruses around before you could weigh it. Most of these tests could detect down to 0.5-5 pg/mL, which we now know is about 270 thousand IU/mL or 5.4 log IU/mL. Any lower viral load was reported as "negative." How does this compare to other viruses? For hepatitis C, a high viral load is 200 thousand IU/mL. For HIV, the viral load is too high to measure if they are over 500 thousand copies/mL. In other words, this early test for hepatitis B viral load was awful!

To complicate matters, there are many different tests for hepatitis B viral load. Each of these test reports their viral load in either copies/mL or rarely, Genome Equivalents (GE)/mL. Indeed, most scientific papers are still reporting viral loads in copies/mL even in 2007. However, even though they used the same units, different tests can give very different results. You may have noticed that this website reports everything in International Units (IU)/mL. This is the new international standard. Whenever you see a viral load report in IU/mL you don't have to worry about which lab did the testing or which company's test kit was used.

Using the older Digene test, we used to think that anyone with a viral load under 5 pg/mL (270 thousand or 5.4 log IU/mL) could not have active disease from hepatitis B. In the early 2000s better tests became available and it became clear that some people with viral loads as low as 1 thousand (3 log) IU/mL could have active hepatitis B disease. At the University Health Network in Toronto, our tests can currently detect down to a level of 6 (0.8 log) IU/mL, which is very low indeed. On the other end, hepatitis B viral loads can go so high they still cannot be measured, over 1 trillion (9 log) IU/mL. With such a large range of numbers, we refer to viral loads in the language of the engineers. Namely, 3 logs is 1 thousand, 6 logs is 1 million, and 9 logs is 1 billion.

We do not confidently know what viral load is safe. Some people believe that any person with a high viral load over 4-5 logs means they are at risk for liver disease and liver cancer. We believe that the viral load is only one test of many. We have to ask what the viral load means in this particular person. For a more detailed discussion about this, see the page on what it means to have chronic hepatitis B infection.

Learning points
  • Viral load testing should be done as part of routine clinical evaluation of people with chronic hepatitis B infection.
  • The range of viral load is very large in hepatitis B, and should be expressed in logs. Just count how many "0s" there are:
    • 1 log - 10
    • 2 logs - 100
    • 3 logs - 1,000 or 1 thousand
    • 4 logs - 10,000
    • 5 logs - 100,000
    • 6 logs - 1,000,000 or 1 million
    • 7 logs - 10,000,000
    • 8 logs - 100,000,000
    • 9 logs - 1,000,000,000 or 1 billion

We should not look at the viral load alone. We should ask what does the viral load mean in this particular person with hepatitis B.

Examples:


  • A very high viral load over 9 logs is not very risky in those who are young - no damage is being done
  • A moderate viral load of 5-6 logs may be associated with a lot of liver damage
  • A low viral load of 2-3 logs may not stay low over time and therefore may be risky
  • An undetectable viral load < 12 IU/mL may become high if the immune system is suppressed

It is important to be familiar with all these hepatitis B proteins because all of our tests and many of our new treatments are based on the structure of the virus. If you want to learn more about these specific tests, you can go on to learn about the details about HBsAg/anti-HBs, or HBeAg/anti-HBe testing.


You can move on to learn about chronic hepatitis B infection or go back to the main page on hepatitis B tests.