Tests for viral hepatitis
Antigen and Antibodies
An antigen is a foreign or ‘invading’ toxin or substance that enters the body. Your body’s immune system defends against antigens by producing special proteins that bind to the invader to destroy them. These are antibodies, also known as immunoglobulins (Ig).
The production of antibodies against antigens is known as your ‘immune response’. Many of the following tests are used to measure your immune response to certain viruses – this will tell the doctor if you have been exposed to that virus in the past. Further tests will assess whether you still have the virus or whether your body has got rid of it.
In an acute infection your immune system produces a type of antibody called IgM. This means you have only recently been infected. If you have been infected in the past or have a chronic infection you will have a type of antibody called IgG.
This test detects whether you have produced antibodies known as immunoglobulin M and immunoglobulin G against the hepatitis A virus (HAV).
Remember too that the test will also come back positive for IgG if you have had the hepatitis A vaccination. It is presumed that one infection with hepatitis A produces lasting immunity (protection) against further infection.
If you’ve been diagnosed with hepatitis A, you can find out more about the condition, how to manage it and how best to look after yourself by downloading our publication on hepatitis A
Most people who come into contact with hepatitis B (HBV) will ‘clear’ the virus during the first six months of their infection. During this phase, the condition is known as acute hepatitis B. People who do not clear the virus after six months will be diagnosed as having chronic (long-term) hepatitis B, which can cause liver damage.
Tests are carried out to look for antigens and antibodies in your blood. The results of these may indicate several possibilities:
- you have been infected by the virus in the past
- you have a new infection
- the infection is likely to go away by itself
- the infection has become chronic (long-term).
These antigens and antibodies are known as serological or viral ‘markers’. Doctors will look for markers in your blood over the course of your infection to see how the virus is progressing and/or responding to treatment. In particular, finding ‘surface’ and ‘e’ antigens known as HBsAg and HBeAg and their corresponding antibodies will help your healthcare team understand more about the pattern of your disease, and how it’s likely to progress
This is a test to find out if you have a current infection. HBsAg is the earliest sign of the virus and disappears from your blood as the infection clears. A positive result indicates infection. If the antigen is not found (negative result), this shows that either you have never been exposed to hepatitis B or that you have recovered from infection and cleared the virus. The term ‘surface’ refers to the outer surface of the virus itself.
This test is used to confirm the presence of HBeAg, which only appears in the blood when the virus is present and is a sign that you are actively making the virus (and therefore able to pass it on to others). What happens after this antigen is found will depend on how quickly your immune system produces antibodies called anti-HBe.
This is the test that looks for the anti-HBe antibody produced in response to the hepatitis B e antigen (although anti-HBe is also present in people recovering from acute hepatitis B infection).
In chronic hepatitis B, a positive result usually suggests that only low levels of the virus are likely to be present in your blood.
The anti-hepatitis B core antigen is an antibody to the ‘core’ part of the hepatitis B virus, the hepatitis B core antigen. However, this antibody does not provide the protection usually associated with antibodies and is found in people with acute infection, in chronic carriers and in people who have cleared the infection.
Doctors will use the results of other tests to interpret the presence of anti-HBc in your blood.
This important test does not look for antigens or antibodies but monitors the amount of virus in your blood, known as your ‘viral load’. The higher your viral load, the more active your infection will be. Active virus replication, where the virus is making lots of copies of itself, is known as positive HBV DNA. Doctors will be looking for a very low amount or no trace of the virus as a marker of your response to antiviral medication.
Hepatitis B treatments are very effective and can completely suppress the virus in most cases although they don’t usually get rid of it completely. If you are on these medicines it is very important not to miss doses as you cause the virus to become resistant. Luckily they generally have very few side effects. They are also safe in pregnancy.
If you’ve been diagnosed with hepatitis B, you can find out more about the condition, how to manage it and how best to look after yourself by downloading our publication on hepatitis B
As with hepatitis B, a number of tests will be carried out when you are suspected of having hepatitis C
(HCV) or after the virus has been diagnosed. They will be used to follow its progression and to check
on your response to treatment. There are now effective treatments available for hepatitis C so it’s
important to get tested if you have ever been at risk.
An anti-HCV test looks for any trace of antibodies in your blood. If they are found, this shows that you
have been exposed to the hepatitis C virus. This test is unable to reveal whether you have active viral
An HCV-RNA test detects the hepatitis C virus in your blood and indicates whether this is an active
infection. The presence of HCV viral RNA is a ‘positive’ result while its absence will be ‘negative’. This
test may also be used as a follow-up to your treatment to see if you have cleared the virus from your
This test measures the number of viral RNA particles in your blood. Doctors will usually perform these tests over the course of your treatment. Measuring your viral load before and after treatment will show how effectively (or not) the treatment is working.
Viral genotyping is carried out to identify the types of hepatitis C virus. There are six major types,
known as ‘genotypes’. The most common in the UK is genotype 1.
Treatments are slightly different for different genotypes, and vary between 8 and 16 weeks depending on things like your viral load, whether you have cirrhosis or not and if you have been treated before.
The modern treatments for HCV are very effective with few side effects. Most people treated go on to be permanently cured of the virus.