Question

Which of the following is routinely performed to detect typhoid?

• A. Widal test
• B. ELISA
• C. Gel electrophoresis
• D. RT-PCR

Hint:

Remember standard diagnostic tests from the NCERT syllabus:
- Typhoid $\to$ Widal test
- AIDS $\to$ ELISA (screening) and Western Blot (confirmatory)
- Tuberculosis $\to$ Mantoux test
These are frequently asked in competitive medical entrance exams.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks us to identify the diagnostic test routinely used to detect Typhoid fever.

Step 2: Key Formula or Approach:
Typhoid fever is a bacterial infection caused by Salmonella enterica serovar Typhi.
Let's review the diagnostic tools listed:
1. Widal test: A classic serological agglutination test specifically designed to detect antibodies against the O (somatic) and H (flagellar) antigens of Salmonella typhi in a patient's serum.
2. ELISA: Used for various viral and bacterial infections (like HIV), but not the primary classic routine test for typhoid.
3. Gel electrophoresis: A method to separate DNA, RNA, or protein molecules based on size, not a direct clinical diagnostic test.
4. RT-PCR: Used primarily for detecting RNA viruses (such as SARS-CoV-2).

Step 3: Detailed Explanation:
- Typhoid is contracted through contaminated food or water.
- Clinically, the infection is diagnosed using the Widal test, which is highly cost-effective and routinely performed in healthcare settings, especially in developing countries.
- During the test, the patient's blood serum is mixed with dead Salmonella bacteria containing specific antigens. If antibodies are present, visible clumping (agglutination) occurs.
- Therefore, the Widal test is the correct diagnostic option.

Step 4: Final Answer:
The correct diagnostic test for typhoid is the Widal test, which corresponds to option (A).