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2 main antigens that are used in serology, 3 antigens in total that are found in the hepatitis B virus
Surface antigen (HBsAg)
- Found on the surface of the hepatitis B virus
- If we find this antigen in the blood then we know this person is actively infected either acutely or chronically
- The vaccine for hepatitis B is a modified form of this surface antigen
- PATIENT IS INFECTIOUS
E antigen (HBeAg)
- Found between the core and the surface of the hepatitis virus
- Released during replication – “E antigen escapes”
- If you find this antigen in the blood, it implies that the person is acutely infected with hepatitis B
- Levels of this antigen also correlate to how infective the person is, the higher it is, the more infective they are to others
Core antigen (HBcAg)
- Found in the core of the virus
- Not found in the blood
- Not used as a test
3 main antibodies that correspond to the 3 antigens of the hepatitis B virus
Surface antibody (anti-HBs)
- Demonstrates an immune response to the HBsAg
- A positive surface antibody could mean
- RESOLVED PRIOR INFECTION
- RECEIVED HEPATITIS B VACCINE
E antibody (anti-HBe)
- Demonstrates that the patient at one point was infected with this virus where the virus was actively dividing and thus releasing the E antibody
- A positive E antibody could mean
- RESOLVED PRIOR INFECTION
Core antibody (anti-HBc)
- 2 versions: IgM and IgG
- IgM version implies an acute infection
- High if acute infection (PATIENT IS INFECTIOUS)
- IgG
- If positive but HBsAg is negative then this implies
HBV DNA
- Direct count of copies of the virus
- Also called the viral load
HOW TO DETERMINE IF SOMEONE HAS SIMPLY BEEN VACCINATED INSTEAD OF A RESOLVED PRIOR INFECTION?
- Anti-HBs antibody positive indicating that the patient has developed antibodies against either the surface antigens from a vaccine or from a prior infection (so we know there is immunity in general)
- Anti-HBc antibody negative indicating that the patient has never been infected with hepatitis B (because remember we never inject the core in a vaccine, just the surface antigen)
What is typical outpatient testing for hepatitis B look like in PublicHealth Ontario? (from PublicHealth Ontario directly)
- If HBsAg is reactive, further testing for Anti-HBc (Total) is performed automatically
- If HBsAg is reactive, but the anti-HBc (total) is non-reactive then the specimen is tested using a HBsAg confirmatory test (‘blocking assay’).
- If the HBsAg and anti-HBc (total) are both reactive and the patient has acute symptoms indicated on the requisition, then the specimen will have the following tests performed:
- HBeAg
- anti-HBe
- anti-HBc IgM