**Question:** A 30-year-old patient presented with a history of jaundice for 10 days. His liver function tests showed bilirubin of 10 mg/dl, SGOT/SGPT - 1100/1450, serum alkaline phosphatase -240 IU. He was positive for Hbs Ag. What should be the confirmatory test to establish acute hepatitis B infection -

A. HBeAg
B. Anti-HBe
C. HBsAg
D. Anti-HBc

**Correct Answer:** C. HBsAg

**Core Concept:**
Hepatitis B virus (HBV) is a hepatotropic virus that causes acute, chronic, and fulminant hepatitis. One of the key markers for acute hepatitis B infection is the presence of Hepatitis B surface antigen (HBsAg). HBsAg is produced early in the course of infection and remains positive throughout the entire acute phase.

**Why the Correct Answer is Right:**
In the context of the patient's clinical presentation and laboratory findings, the correct confirmatory test for acute hepatitis B infection is Hepatitis B surface antigen (HBsAg). The patient has been tested positive for HBsAg, indicating acute hepatitis B infection.

**Why Each Wrong Option is Incorrect:**

A. HBeAg is a marker for active viral replication and is typically found in the early stages of acute and chronic hepatitis B infection. However, it is not a confirmatory test for acute hepatitis B infection.

B. Anti-HBe is an antibody against HBeAg, and is usually present when HBeAg is negative. It is not a direct confirmatory test for acute hepatitis B infection.

D. Anti-HBc is an antibody against hepatitis B core antigen (HBcAg), which is present during the entire course of hepatitis B infection, but it is not a direct confirmatory test for acute hepatitis B infection. Confirmation of acute hepatitis B infection requires the presence of HBsAg and either HBeAg or anti-HBe.

**Clinical Pearl:**
In the clinical setting, it is essential to consider hepatitis B infection in patients presenting with jaundice and abnormal liver function tests, especially if they are positive for HBsAg and HBeAg. A negative HBeAg and anti-HBe test results suggest chronic hepatitis B infection, while a positive HBsAg test indicates acute hepatitis B infection. The combination of positive HBsAg and either HBeAg or anti-HBe confirms the diagnosis of acute hepatitis B infection.