This is a guideline which outlines the diagnosis and management of Hepatitis B in adults and children.
Of most importance to us, they advise that after you get a positive Hepatitis B test result back on a patient (Hepatitis B surface antigen - HBsAg), certain further tests should be done. The results of these tests should be included in the referral. This probably alters management in that previously we would probably have referred patients on at that first positive test. I would encourage people to follow local guidance on this. Remember that there is NICE guidance on when to do Hep B testing. The tests NICE advises are:
- Hepatitis B e Antigen (HBeAg) and anti-HBe
- HBV DNA level (Hepatitis B viral load)
- IgM antibody to Hepatitis B core antigen (anti-HBc IgM)
- Hep A / Hep C / Hep delta / HIV antibodies
- GGT (gamma GT)
- Clotting studies
- Liver ultrasound
The other bit of importance to us is that pregnant women who are HBsAg positive should be referred to a specialist, as they will need treatment in the third trimester to avoid vertical transmission. The rest of the guideline is aimed at specialists.
Some of the background science was new to me and it helps to explain why these tests are needed and why patients go on to have the treatments they do, so read on if you want to know more...
Those pesky antigens and other confusions...
- HBV DNA is used to look at the viral load. Higher levels suggest a greater risk of complications.
- HBsAg looks for the 's' antigen on the surface of the virus. It is a marker of acute or chronic infection, but gives no indicator of the chance of complications.
- HBeAg looks for the 'e' antigen which is a marker of viral replication. Most of the time, if you have this, it signifies a higher risk of complications as the viral load will increase when it is replicating. Sometimes however the virus doesn't produce HBeAg at all.
- HBsAg seroconversion (ie you have anti-HBsAg). This is when you produce antibodies to the HBsAg and clearance of the virus follows, curing the infection. Remember, if you are vaccinated, but haven't been infected, you will show anti-HBsAg, but not the HBsAg.
- HBeAg seroconversion (ie you have anti-HBeAg). This is when you produce antibodies to the HBeAg. This is a good sign as normally it means that the body is starting to stop the replication of the virus. Usually the patient then goes into a carrier state. You are aiming to induce this state through treatment.
What happens when you get infected...
- You start to show HBsAg
- You may either clear the virus, or it may remain inactive, or or it may replicate, giving an increased viral load and hence causing complications.
- Complications include liver fibrosis, cirrhosis and hepatocellular carcinoma.
- Treatment aims to suppress HBV replication, thus allowing your body to fight it, produce antibodies and therefore pass into a carrier state. This will then reduce the risk of complications.
- Sometimes, the virus then mutates and will start replicating again, even after treatment.