Which Antigen is involved in hepatitis B transmission?

Appeared in: Central Institute of Psychiatry - 9 July 2022

Explanation

HBsAg stands for Hepatitis B surface antigen, which is the protein on the outer surface of the Hepatitis B virus.
The presence of HBsAg in the blood is the primary marker used to diagnose an active Hepatitis B infection.
A person who tests positive for HBsAg is considered infectious and can transmit the virus to others through blood or other body fluids.

Option A: This is a general term. While HBsAg is a surface antigen, the question requires the most specific and standard term used in clinical practice.
Option B: The Hepatitis B core antigen (HBcAg) is part of the internal structure of the virus and does not circulate freely in the bloodstream. Therefore, it cannot be tested to determine infectivity.
Option C: This term is confusingly worded and likely refers to an antibody (e.g., Anti-HBs). Antibodies are part of the immune response and indicate protection (immunity) or past exposure, not active infection or transmissibility.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hepatitis B serological markers and transmission as background academic context rather than a clinical decision trigger.
HBsAg screening is a critical public health measure for all blood and organ donors to prevent transmission to recipients.
Screening pregnant women for HBsAg is essential to identify newborns who require Hepatitis B immune globulin (HBIG) and the HBV vaccine at birth to prevent perinatal transmission.
Healthcare workers must be aware of their HBsAg status and vaccination history (confirmed by Anti-HBs levels) to ensure safety and guide post-exposure prophylaxis (PEP) decisions after a needlestick injury.

How to Approach the Question

First, identify the core of the question, which is asking for the specific viral component (antigen) that indicates a person can transmit Hepatitis B.
Recall the different serological markers for Hepatitis B. Differentiate between antigens (parts of the virus itself) and antibodies (the body's immune response). The question asks for an antigen.
Evaluate each option. 'Anti hep-B antigen' is likely an antibody, so it can be eliminated. 'Core antigen' (HBcAg) is not found in the blood.
You are left with 'Surface antigen' and 'HbsAg'. Recognize that HBsAg is the specific, standard medical abbreviation for the Hepatitis B surface antigen.
In medical and nursing questions, always choose the most precise and specific correct answer. Therefore, HBsAg is a better choice than the general term 'Surface antigen'.

Concept Tested & Keywords

QuK4EYKN711ZNth6Z_xukC

E6 Medicine Harrison 22e Part 2 pp. 548-550, 561-563

Practise the full Central Institute of Psychiatry - 9 July 2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.