Interpreting Hepatitis B Serology

Introduction

• Presenter: Tom from Zero Finance
• Focus: Simplifying the understanding of hepatitis B serology.
• Importance: Common exam topic and relevant in clinical practice.
• More info available at: zero to finals

Basic Understanding of Antibodies

• Antibodies: Proteins produced by B-cells.
• Each B-cell produces a single type of antibody targeting a specific antigen.
• Antigens: Proteins that can be part of viruses, bacteria, fungi, cancers, or body's own cells (autoimmune disease).
• Antibodies attach to antigens and help the immune system attack.

Hepatitis B Virus Antigens

1. Surface Antigen (HBsAg)
   • Found on the surface of the virus.
   • Positive result indicates infection.
   • Used in vaccinations to trigger immune response.
2. E Antigen (HBeAg)
   • Found between the core and surface.
   • Released during replication, indicating high infectivity.
3. Core Antigen (HBcAg)
   • Found inside the virus core.
   • Not useful in blood tests as it does not circulate.

Hepatitis B Virus Antibodies

1. Surface Antibody (anti-HBs)
   • Indicates immune response to surface antigen.
   • Positive result could indicate vaccination or past infection.
2. E Antibody (anti-HBe)
   • Responds to E antigen.
   • Negative antigen but positive antibody indicates past active replication.
3. Core Antibody (anti-HBc)
   • IgM indicates acute infection.
   • IgG lingers, indicating past infection.

Testing and Interpretation

• Hepatitis B DNA: Tests for the viral load and gives a count of viral copies.
• Screening:
  • Check for Hep B core antibody (previous infection).
  • Check for Hep B surface antigen (active infection).
  • If positive, test for E antigen and B DNA for infectivity and viral load.
• Vaccine Note: Positive surface antibody could mean prior vaccination, not an active infection.

Conclusion

• Hepatitis B serology is useful in both exams and practice.
• For more resources, visit Zero to Finals website for notes, tests, and a blog on medical careers.
• Support the channel on YouTube with likes, comments, and subscriptions.