The serological marker of acute Hepatitis B infection is –
**Core Concept**
Hepatitis B is a liver infection caused by the Hepatitis B virus (HBV), which can lead to acute or chronic infection. The serological markers of HBV infection are crucial in diagnosing and monitoring the disease. These markers include surface antigen (HBsAg), surface antibody (HBsAb), core antibody (HBcAb), and e-antigen (HBeAg).
**Why the Correct Answer is Right**
The correct answer is IgM anti-HBc (Immunoglobulin M antibody to Hepatitis B core antigen). This marker indicates an acute Hepatitis B infection. IgM anti-HBc is produced in response to the core antigen of HBV and is detectable in the blood during the acute phase of the infection. It is a sensitive marker for acute HBV infection and is often used in conjunction with other markers to confirm the diagnosis.
**Why Each Wrong Option is Incorrect**
**Option A:** HBsAg (Surface antigen) is a marker of active HBV infection, but it can also be present in chronic infection. It is not specific for acute infection.
**Option B:** HBsAb (Surface antibody) is a marker of immunity to HBV, either from vaccination or past infection. It is not a marker of acute infection.
**Option C:** HBeAg (e-antigen) is a marker of viral replication and increased infectivity. While it is associated with acute infection, its presence is not as specific for acute HBV infection as IgM anti-HBc.
**Clinical Pearl / High-Yield Fact**
Remember the "ABC rule" for Hepatitis B serology: HBsAg (A) indicates active infection, HBsAb (B) indicates immunity, and IgM anti-HBc (C) indicates acute infection.
**Correct Answer:** C. IgM anti-HBc