This is always a classic exam question so good to know. It is not difficult to learn once the basics are known.
You need to know what the following mean: HBsAg, anti-HBs, HBeAg, anti HBe, anti-HBc and IgM anti-HBc.
Hepatitis B surface antigen (HBsAg): This is a protein on the surface of the hepatitis B virus (HBV); it can be detected in the serum during acute or chronic HBV infection. The presence of HBsAg indicates that the person is infectious. HBsAg is the antigen used to make Hepatitis B vaccine.
Hepatitis B e antigen (HBeAg): A product of the nucleocapsid (envelope) gene of the hepatitis B virus that is found in serum during acute and chronic hepatitis B infection. Its presence indicates that the virus is replicating and the infected person has high levels of HBV. However patients that are HBeAg negative may also have high levels of HBV.
Hepatitis B surface antibody (anti-HBs): The presence of anti-HBs is generally interpreted as indicating recovery and immunity from HBV infection. Anti-HBs also develops in a person who has been successfully vaccinated against hepatitis B.
Total hepatitis B core antibody (anti-HBc): Appears at the onset of symptoms in acute hepatitis B infection and persists for life. The presence of anti-HBc indicates previous or ongoing infection with HBV. In the laboratory setting it is also a very good “control” for a positive HBsAg result. Except occasionally in early infection, if the HBsAg is positive, then the anti-HBc must be positive also.
IgM antibody to hepatitis B core antigen (IgM anti-HBc): Its presence usually indicates acute as opposed to chronic Hepatitis B infection.
Hepatitis B e antibody (HBeAb or anti-HBe): Spontaneous conversion from e antigen to e antibody (a change known as seroconversion) is a predictor of long-term clearance of HBV in patients undergoing antiviral therapy and indicates lower levels of HBV.
Here is a graph of what happens to the levels of these markers in acute resolving Hepatitis B infection:
and here is what happens to the markers in chronic hepatitis B infection:
You then need to be aware of what the typical “marker pattern” is in common clinical scenarios.
The tricky one is the last scenario in the table, “Core alone positive”, which is seen from time to time. An HBVDNA level can be useful to clarify between he possibilities.
….and finally, I recommend you consolidate your knowledge by doing the excellent case studies on this topic on the CDC website. Click here.
(Note that these case studies also include interpretation of other Hepatitis serology assays eg HAV, HCV and HEV, which is all fairly starightforward compared to Hepatitis B)
Click here for a few MCQs on Hepatitis B serology