If you have recently been diagnosed with chronic hepatitis B, your liver specialist is running a series of tests over time to determine if you are a good candidate for treatment. Remember, not everyone benefits from treatments currently available to chronic HBV patients.
Since you are chronically infected, you know your hepatitis B panel most likely shows that you are:
The last entry in this series looked at the HBeAg (HBe-antigen) and HBeAb (or anti-HBe antibody) tests, and what they mean if they are positive or negative, giving you a good indication of the replication activity of the virus and how infectious you are. The HBV DNA test or viral load test takes this a step further by quantifying the amount of HBV DNA you have at the time of the blood draw.
Simply put, the HBV DNA test indicates how much of the HBV virus is circulating in your blood. This test, over time, can give a good idea of the hepatitis B replicative activity in your liver. The virus is released into your blood, which can then drawn and analyzed by the HBV DNA viral test.
These viral load test results may be used to help determine whether or not treatment is recommended. If you are HBeAg negative, and your viral load is above 2,000 IU/mL, treatment may be recommended. If you are HBeAg positive, treatment may be recommended if your viral load is above 20,000 IU/mL. Please note that these are guidelines. There are other factors that come into play when recommending treatment, such as ALT and other liver function tests, liver diagnostic information, age, family history, and more. It can be complicated, so the importance of a liver specialist cannot be underestimated.
The viral load test results may also be monitored to determine treatment response. This is particularly true with the use of antivirals. Antivirals work by stopping replication of the virus. If your viral load decreases significantly or becomes undetectable, then you are having a favorable response. If your viral load goes down and eventually begins to elevate again, then it may indicate that you have developed a resistance to the antiviral you are taking.
The HBV DNA test is performed using a Polymerase Chain Reaction (PCR), a technique used for rapidly generating DNA fragments so your HBV DNA can be analyzed. It’s a sophisticated, but common test, and it’s a complicated if you don’t work in the lab. There are different techniques, so you will likely see reference to the method used for your test such as “real time” (RT) PCR or TAQMAN. This shouldn’t really matter unless you are in a clinical trial, where consistency is very important when analyzing results.
What does matter for comparative purposes are the units of measurement. The viral load test is typically measured in the units IU/mL or international units per milliliter. Previously it was measured in copies per milliliter, and sometimes those units are still used. When comparing, it is important to be sure the units are consistent from one test to the other. In case they differ, there are about 5 to 6 HBV DNA copies per international unit, so you can do a basic conversion and compare your results over time. Remember to keep copies of your lab information on file so you can track your status. An Excel spreadsheet works great.
The sensitivity of the HBV DNA test may vary with the lab, but the low end of the range is typically 300 IU/mL or less. Below the threshold of the test, the viral load is considered “undetectable” – something everyone with chronic hepatitis B wants to hear.
How the results of the test are displayed mathematically on your lab results can be confusing. Because the amount of virus in the blood may be very high – in the millions or billions, the result they may be displayed as an exponent or a log, rather than a whole number. If this is confusing to you, please take a look at this explanation on the math.
The range of the viral load numbers vary greatly from person to person, and over time the viral load will likely vary with each individual. Young children may have viral loads in the hundreds of million or even billions. It sounds scary, but that is not unusual, and kids have different treatment guidelines. The viral load may remain very high for decades depending on how your body is responding to the virus. This varies with the person and the genotype.
It is important to remember that the viral load test provides you with important information, but it must be read in relation to your other HBV and liver function test results in order to determine if treatment is a good option, or if you are responding favorably to current treatment. Although an undetectable or low viral load is considered favorable, it does not necessarily guarantee that you have not, or are not experiencing liver damage. Hepatitis B is a tricky virus. Talk to your liver specialist with your HBV specific questions.