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15. What are the serological markers for hepatitis B?

These are the serological markers that are available in our laboratories. The surface antigen, now even for our physician colleagues, it’s hard to even pronounce these tests, because this is the hepatitis B surface antigen, and that’s a mouthful, so I always tell the students to just call it surface antigen- two words, easy to say. Sometimes they call it HBIG, HBsAg, it’s all hard to say, just call it surface antigen. The surface antigen is the marker of infection, it’s the first thing that appears in a person that’s infected, and by arbitrary convention, if it sticks around for more than 6 months, we call that chronic hepatitis B. So that individual, if they have gotten infected as an adult, aren’t getting rid of it, it’s become chronic. E-antigen indicates active replication except in the precore and core promoter mutants where it’s absent. The surface antibody is recovery or immunity so that if an individual had natural infection and then cleared, they will have a surface antibody. This is also the antibody that you get after your vaccination, because when you get hepatitis B vaccine, you’re vaccinated with purified surface antigen. It’s recombinant, it’s made in the laboratory, and that leads your immune system to develop a surface antibody against that surface antigen. And once in a while, to make things even more confusing, people who are chronically infected and have the surface antigen may also have the surface antibody, now that really causes a lot of confusion and happens in about 10% of individuals. It has no particular relevance; it just is a little confusing. The e-antibody we’ve already talked about generally indicates inactive virus, except in the precore. Now the core antibody is a little more confusing, because this indicates present or past infection, so that when you’re infected with hepatitis B, you will develop the surface antigen right away, and right away, you’ll develop the core antibody. If you go on to recover from hepatitis B, you will lose the surface antigen and develop the surface antibody, but the core sticks around. The core antibody comes right when you’re infected, and it sticks around for the rest of your life. People who have natural immunity will have both antibodies, the surface antibody and the core antibody. People who get the vaccine shot and are protected will only have one antibody, the surface antibody.