If you have been diagnosed with chronic hepatitis B, your doctor has probably run several blood tests that show if the infection is harming your liver and identify what stage of infection you are in. Doctors consider all of these results when deciding if you need treatment and how often you should be monitored.
In this blog, we’ll examine how one of the tests — the HBV DNA or viral load test –can give you a snapshot into your hepatitis B infection and your health. The HBV DNA test is performed on a blood sample using a Polymerase Chain Reaction (PCR) technique that rapidly generates HBV DNA fragments so they can be measured. Today, viral load is usually measured using international units per milliliter (IU/mL). However, in the past it was measured in copies per milliliter (copies/mL), and in some regions and labs, it is still used.
If you ever need to convert copies into international units, there are about 5.6 copies in one international unit, so 5,000 copies/mL equals about 893 IU/mL. Remember to keep copies of your lab information on file so you can track your status. An Excel spreadsheet works great.
The sensitivity of HBV DNA tests may vary with each lab so it’s a good idea to always use the same lab for your test. Labs usually measure down to about 300 IU/mL. Below that threshold, the viral load is considered “undetectable” – something all of us with chronic hepatitis B wants to hear.
How HBV DNA results are presented mathematically on your lab report can be confusing. Because the amount of virus in the blood may be very high – in the millions or billions – the result 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.
What does viral load say about what stage of hepatitis B you are in? Your viral load also varies over time, depending on your age and “stage” of infection.
Children and adults in the “immune tolerant” stage can have viral loads in the millions or even billions. It sounds scary, but it’s not unusual. Your viral load can remain very high for decades until your immune system begins attacking the infection. Most children and young adults who test positive for the hepatitis B “e” antigen (HBeAg) generally have high viral loads, generally doctors don’t treat patients in this stage. Once their immune systems get rid of HBeAg and generate “e” antibodies (HBeAb), their viral loads begin to decline.
Adults with undetectable or low viral loads and no signs of liver damage are in an “inactive” stage. Adults with normal ALT (SGPT) levels, which indicate no current liver damage, and undetectable or viral loads less than 2,000 IU/mL generally do not require treatment.
People in the “active” stage with elevated viral loads and signs of liver damage need treatment. Many people in their 40s, 50s or 60s, develop HBeAg-negative hepatitis B. Though individuals may have lost HBeAg, the virus has mutated over time and is able to keep replicating, putting these older patients at risk of liver damage. Doctors recommend antiviral treatment if these patients’ viral load exceeds 2,000 IU/ML and their ALT levels are elevated.
Why is it important to measure HBV DNA during treatment? When daily antiviral pills (either tenofovir or entecavir) are prescribed, doctors measure your HBV DNA to see if the drug is working to reduce your viral load. Antivirals work by meddling with the viral DNA so the virus cannot reproduce effectively. Doctors measure your viral load to make sure the antiviral is working.
Why is measuring viral load important if you’re pregnant? Today, all pregnant women are screened for hepatitis B, and experts also want their viral loads to be measured. When pregnant women have high viral loads—exceeding 200,000 IU/mL—medical guidelines recommend antiviral therapy during their third trimester of pregnancy to reduce their risk of infecting their newborns. Babies born to HBV-infected women can become infected even if they are immunized at birth and treated with HBIG (hepatitis B antibodies) if their mothers have high viral loads.
It is important to remember that a viral load test provides you with important information, but it must be considered in relation to your other HBV and liver function tests results to determine if treatment is needed at all, or if you are responding favorably to current treatment. Although an undetectable or low viral load is good news, it does not necessarily guarantee that you have not, or will not experience liver damage. Hepatitis B is a tricky virus. Talk to your liver specialist about all of your test results.