Diagnosis of typhoid is done by?

Appeared in: MNS 2015

Explanation

The Widal test is a classic serological agglutination test used for the diagnosis of enteric (typhoid) fever.
It works by detecting the presence of antibodies in the patient's serum that bind to the O (somatic) and H (flagellar) antigens of the Salmonella typhi bacterium.
A diagnosis is suggested by a significant rise in antibody titers in paired samples or a single high titer in an endemic setting, although its use has limitations.

Option A: ELISA is a general laboratory technique, not a specific test for typhoid. While ELISA-based kits for typhoid exist, the Widal test is the historically recognized and specific serological test for this disease among the choices.
Option C: The VDRL (Venereal Disease Research Laboratory) test is a non-treponemal test used for screening for syphilis.
Option D: The Lepromin test is a skin test used to classify the type of leprosy a person has (tuberculoid vs. lepromatous) by assessing their cell-mediated immunity to the leprosy bacillus.

Clinical Relevance

Nursing practice connection: Use the key finding related to Diagnostic methods for infectious diseases, specifically Typhoid (Enteric) Fever to guide bedside assessment, documentation, and the next nursing action.
Nurses should understand that while the Widal test is common, its reliability is limited. False positives can occur due to prior vaccination or cross-reactivity with other bacteria, and false negatives can occur early in the illness.
The gold standard for typhoid diagnosis is blood culture, which is most sensitive during the first week of fever. A nurse's role includes ensuring blood samples are collected aseptically, preferably before starting antibiotic therapy, to maximize diagnostic yield.
Patient education is key. Nurses should explain the importance of completing the full course of antibiotics for typhoid to prevent complications, relapse, and the development of a chronic carrier state.

How to Approach the Question

First, identify the key concept in the question: the diagnostic test for 'typhoid fever'.
This is a factual recall question that requires matching a specific disease to its corresponding laboratory test.
Systematically review each option provided.
Eliminate options associated with other diseases. You should recognize VDRL is for syphilis and the Lepromin test is for leprosy.
Differentiate between the remaining options. ELISA is a general testing platform, whereas the Widal test is a specific, named test historically linked to typhoid diagnosis.
Select the most specific and appropriate test for the disease mentioned in the stem, which is the Widal test.

Concept Tested & Keywords

Concept Tested: Diagnostic methods for infectious diseases, specifically Typhoid (Enteric) Fever.
Stem keywords: Diagnosis, typhoid
Lead-in keywords: BEST, MOST RELEVANT CLUE
Negative lead-in flag: false

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

Practise the full MNS 2015

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