**Question:** A 2 month baby presents with history of jaundice, turmeric colored urine and pale stools since birth. Examination reveals liver span of 10 ems. The most specific investigation for establishing the diagnosis would be -

A. Serum Bilirubin
B. Liver function tests
C. Hepatitis B virus antigen
D. Hepatitis C virus antibody

**Correct Answer:** .

**Core Concept:**
The presented case describes a two-month-old infant with clinical features suggestive of neonatal jaundice, which is a condition characterized by the abnormal accumulation of bilirubin in the blood, leading to yellow discoloration of the skin and mucous membranes. Jaundice is commonly observed in infants due to normal physiological processes such as breastfeeding, but when persistent or accompanied by other symptoms, it may indicate an underlying liver disorder.

**Why the Correct Answer is Right:**
In this scenario, the most specific investigation to establish the diagnosis would be:

1. Serum Bilirubin (Option A): Bilirubin is a product of heme catabolism in the liver, and elevated bilirubin levels can indicate impaired liver function or dysfunction. Therefore, measuring serum bilirubin levels would be an essential step in assessing the infant's liver function and determining the cause of jaundice.

2. Liver function tests (Option B): A broader panel of liver function tests, including enzymes like SGOT, SGPT, and alkaline phosphatase, can provide further insights into the liver's health and functionality. These tests would help differentiate between cholestasis (impairment of bile secretion) and hepatocellular (liver cell) dysfunction.

3. Hepatitis B virus antigen (Option C): Hepatitis B virus antigen is a marker specific to Hepatitis B infection, which is a rare cause of neonatal jaundice. This option is less relevant in this scenario as the primary concern is jaundice in a neonate, and hepatitis B is less common in neonates.

4. Hepatitis C virus antibody (Option D): Similar to Option C, Hepatitis C virus antibody is a marker specific to Hepatitis C infection, which is also a rare cause of neonatal jaundice. This option is less relevant in this scenario as the primary concern is jaundice in a neonate, and Hepatitis C is less common in neonates.

**Why Each Wrong Answer is Incorrect:**

Option C and D (Hepatitis B and C virus markers) are less relevant in neonates as the incidence of these infections is relatively low in this age group. Additionally, neonatal jaundice usually resolves within the first few weeks of life, regardless of infection status.

The correct investigations are focused on evaluating liver function and excluding underlying liver issues in the neonate:

1. Serum Bilirubin: Elevated serum bilirubin levels indicate impaired liver function and bile secretion. This test is essential for evaluating the neonate's liver function and determining the cause of jaundice.

2. Liver function tests (LFTs): These tests, including SGOT, SG