Hepatitis B Serology

Question 1

What are the antigens and what do they mean?

Answer 1

• Surface antigen (HBsAg) is the first marker to appear and causes the production of anti-HBs
• HBsAg normally implies acute disease (present for 1-6 months)
• If HBsAg present > 6 months, implies chronic disease (i.e. Infective)
• Anti-HBs implies immunity (either exposure or immunisation). It is negative in chronic disease

Positive Anti-HB’s’ = ‘Safe’ (Previous vaccination)

• Anti-HBc implies previous (or current) infection, can get two types IgM or IgG
• IgM anti-HBc appears during acute/recent hepatitis B infection IgM –> an infection in the Moment (acute)
• IgG anti-HBc persists, IgG –> The infection is a Grandpa, has been around for a while

Positive Anti-HB’c’ = Caught (Currently infected)

• HbeAg results from breakdown of core antigen from infected liver cells as is, therefore, a marker of infectivity. Marker of HBV replication and infectivity

Question 2

Example results

Answer 2

• Previous immunisation: anti-HBs positive, all others negative
• Previous hepatitis B (> 6 months ago), not a carrier: anti-HBc positive, HBsAg negative
• Previous hepatitis B, now a carrier: anti-HBc positive, HBsAg positive

Question 3

What are the Hepatitis B antigens?

Answer 3

Surface antigen HBsAg

E antigen HBeAg

Core antigen HBcAg

Question 4

What are the Hepatitis B antibodies?

Answer 4

Surface antibody HBsAb

E antibody HbeAb

Core antibody HBcAb

Question 5

What test do you do see the viral load in the bloodstream?

Answer 5

HBV DNA

Question 6

Surface antigen facts HBsAg

Answer 6

Found on surface of HepB

Blood sample is HBsAg +ve, then active infection

If no Hep B infection, result will be -ve

But, vaccines contain HBsAg → so result will be +ve after vaccination, until immune system clears up antigens

Question 7

E antigen facts

Answer 7

Found between core and surface of HepB virus

Floats in this space and Escapes during replication (HBeAg) – Escapes, E antigen

Therefore if HBeAg +ve → acute active infection, where virus is replicating very quickly

Question 8

How does level of HBeAg correlate with level of infectivity?

Answer 8

Increased HBeAg levels, increased infectivity → more infectious to others

Question 9

Core antigen facts

Answer 9

Found on inside of HepB virus

Does not circulate in blood, so NOT helpful blood test

Question 10

Hep B Surface Antibody facts

Answer 10

HBsAb

Demonstrates immune response to HBsAg

As HBsAg given in vaccines, if HBsAb is present, could mean person is just vaccinated, or current infection

So you use other viral markers to distinguish between two

Question 11

HepB E antibody facts

Answer 11

HBeAb

When HBeAg is -ve but HbeAb is +ve, implies they’ve been through phase where virus is replicating actively, but virus now stopped replicating and patient is less infectious, as there has been good immune response to virus

Question 12

HepB core antibody facts

Answer 12

HBcAb

Shows immune response to HbcAg

This helps distinguish between active, chronic, and past infections

There are two versions of HBcAb - IgM and IgG

Question 13

IgM and IgG HBcAb what do they mean?

Answer 13

IgM - acute infections (infection at the Moment)

IgG - lingers after infections (Grandpa, been around a while), helps protect against same infection in future

If IgG is +ve and HBsAg is -ve, indicates past infection

Question 14

How to test someone you suspect has HepB?

Answer 14

Test for HBsAg - tests for active infection

Test for HBcAb - test for past infection

If these are both +ve, then test HBeAg, to see how infective they are, and any viral replication