Which of the following is also known as australia antigen: September 2006
**Core Concept**
The "Australia antigen" refers to the presence of a specific protein on the surface of the hepatitis B virus (HBV). This antigen, also known as the hepatitis B surface antigen (HBsAg), is a marker of acute or chronic HBV infection.
**Why the Correct Answer is Right**
The Australia antigen is a protein that forms the outer envelope of the hepatitis B virus. It is a key component of the virus's structure and is responsible for its identification and classification. The presence of HBsAg in the blood indicates an active HBV infection, and its absence suggests immunity to the virus. The Australia antigen was first identified in 1965 by Dr. Baruch Blumberg, who isolated it from the serum of an Australian Aboriginal individual.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not refer to the hepatitis B virus or its surface antigen.
**Option B:** This option is incorrect because it is not related to the Australia antigen or hepatitis B infection.
**Option C:** This option is incorrect because it is not the correct name for the Australia antigen.
**Clinical Pearl / High-Yield Fact**
The Australia antigen is a significant marker for hepatitis B infection, and its presence is an important diagnostic criterion for the disease. It is essential to note that not all individuals with HBV infection will have a positive HBsAg test, as some may be in the window period or have a false-negative result.
**Correct Answer:** C. Australia antigen is also known as the hepatitis B surface antigen (HBsAg).