**Question:** Early diagnosis of active hepatitis B infection is done by:

A. Serological markers
B. Liver biopsy
C. Viral load
D. Liver function tests

**Core Concept:** Hepatitis B is a viral infection caused by the hepatitis B virus (HBV), which can lead to chronic liver disease, cirrhosis, and hepatocellular carcinoma. Early diagnosis is crucial for timely intervention and management.

**Why the Correct Answer is Right:**
Correct Answer: D. Liver function tests

Liver function tests (LFTs) are a group of blood tests that evaluate the liver's function. They are essential for diagnosing and monitoring liver diseases, including hepatitis B infection. LFTs usually show abnormalities even before the onset of clinical symptoms, making them crucial for early detection of active hepatitis B infection.

**Why Each Wrong Option is Incorrect:**
A. Serological markers: These tests detect the presence of HBsAg (hepatitis B surface antigen), anti-HBs (anti-hepatitis B surface antibody), anti-HBe (anti-hepatitis B e-antibody), and anti-HBc (anti-hepatitis B core antibody). While serological markers help determine the stage of infection, they do not directly diagnose active hepatitis.

B. Liver biopsy: A liver biopsy involves removing a small piece of liver tissue for examination under a microscope. While liver biopsy can provide histopathological evidence of hepatitis B infection, it is an invasive procedure and may not be required for early diagnosis, especially considering the availability of non-invasive alternatives like LFTs.

C. Viral load: Viral load measures the number of hepatitis B DNA copies in the blood. While viral load quantifies the severity of the infection, it does not directly diagnose active hepatitis.

**Clinical Pearl:** Early diagnosis of active hepatitis B infection relies on a combination of serological markers, LFTs, and sometimes anti-HBe and anti-HBc. Liver biopsy and viral load tests are not essential for early diagnosis but can provide additional information later in the course of the disease.

**Correct Answer: D. Liver function tests**

LFTs, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bilirubin, are crucial for diagnosing hepatitis B virus infection and monitoring the response to treatment. Specifically, elevated ALT levels indicate liver cell damage, which is a common feature in hepatitis B infection.