Which of the following is a diagnostic test for typhoid?

Appeared in: JODHPUR AIIMS SNO-2018

Explanation

The Widal test is a classic serological agglutination test specifically used for the diagnosis of typhoid (enteric) fever.
It detects the presence of antibodies in the patient's serum against the O (somatic) and H (flagellar) antigens of the bacterium Salmonella Typhi.
The test typically becomes positive during the second week of the illness, and a four-fold or greater rise in antibody titer between two samples is considered diagnostic.

Option A: ELISA (Enzyme-Linked Immunosorbent Assay) is a broad testing methodology used for detecting many substances, not a specific test for typhoid itself. While some modern typhoid tests use this method, 'Widal test' is the specific name of the classic diagnostic test for typhoid.
Option B: The Shick test is an intradermal test used to determine a person's immunity or susceptibility to Diphtheria, not typhoid.
Option D: The Mantoux test (or Tuberculin Skin Test) is a screening tool for Tuberculosis (TB). It detects an immune response to the bacterium Mycobacterium tuberculosis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnostic tests for common infectious diseases as background academic context rather than a clinical decision trigger.
Accurate diagnosis of typhoid fever is crucial for initiating appropriate antibiotic therapy and preventing complications like intestinal perforation or hemorrhage.
Nurses should be aware of the timing for the Widal test; it is often negative in the first week of fever. Blood culture is the gold standard for diagnosis, especially in the early stages.
What if a patient is in the first week of a high-grade, step-ladder fever? The Widal test may be falsely negative. The priority investigation would be a blood culture, which has the highest yield in the first week.

How to Approach the Question

This is a factual recall question that tests knowledge of specific diagnostic tests.
First, identify the key terms in the question: 'diagnostic test' and 'typhoid'.
Next, systematically review the options provided.
Recall or deduce the disease associated with each test: Elisa (a method), Shick test (Diphtheria), Widal test (Typhoid), and Mantoux test (Tuberculosis).
Match the test with the disease mentioned in the stem. The Widal test is the specific test for typhoid fever.
Confirm the choice by eliminating the other options as they are used for different diseases.

Concept Tested & Keywords

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E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 267-269

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart B (pp 202-403 of 604) p. 92-94

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Attempt every question from this paper in a timed mock, then review the full solution for each one.