**Question:** A new patient presents with jaundice. Most diagnostic investigation of choice is:

A. Hepatitis panel
B. Liver function tests (LFTs)
C. Serum bilirubin
D. Serum electrolytes

**Core Concept:**
Jaundice is a condition characterized by yellow discoloration of the skin and mucous membranes due to elevated levels of bilirubin in the blood. Bilirubin is a breakdown product of heme catabolism, primarily produced in the liver, which is then conjugated and excreted in bile. Elevated bilirubin levels can be indicative of liver dysfunction or obstruction of bile ducts.

**Why the Correct Answer is Right:**
Bilirubin is primarily produced in the liver and excreted through the bile ducts. When liver function is impaired (e.g., due to hepatitis), there is inadequate conjugation and excretion of bilirubin, leading to its accumulation in the blood. Liver function tests (LFTs) are a comprehensive panel of tests that assess the overall function and health of the liver. Conducting LFTs will provide information regarding the liver's ability to produce and excrete bilirubin, making LFTs the most suitable investigation in this case.

**Why Each Wrong Option is Incorrect:**

A. Hepatitis panel: Although hepatitis might be involved, a hepatitis panel focuses on diagnosing viral hepatitis, not evaluating bilirubin levels or liver function.

B. Liver function tests (LFTs): As mentioned earlier, LFTs are required to assess liver function and bilirubin excretion. However, the question specifically asks for the most suitable investigation for jaundice, and LFTs are not the only option.

C. Serum bilirubin: Measuring bilirubin levels is essential but is not sufficient as it only provides information about bilirubin levels without assessing liver function.

D. Serum electrolytes: Elevated bilirubin levels do not affect electrolyte levels, and serum electrolytes are unrelated to jaundice diagnosis.

**Clinical Pearl:**
In clinical practice, jaundice can be caused by various conditions, including liver diseases, biliary obstruction, or hemolysis. Conducting LFTs allows for a broader evaluation, while measuring bilirubin levels alone does not account for liver function or exclude the possibility of obstructive jaundice. A combination of both LFTs and serum bilirubin levels is crucial for an accurate diagnosis and progression of further management in jaundiced patients.