The Widal test is used to diagnose?

DSSSB - 29 August 2019 (Shift-2)

Applied Microbiology & Infection control

Easy

Appeared in: DSSSB - 29 August 2019 (Shift-2)

Explanation

The Widal test is a serological assay specifically designed to aid in the diagnosis of typhoid fever (enteric fever).
It functions by detecting agglutinating antibodies in the patient's serum against the somatic (O) and flagellar (H) antigens of Salmonella enterica serotype Typhi.
A diagnosis is strongly suggested by a fourfold or greater rise in antibody titers in paired samples collected 7–10 days apart. A single high titer (e.g., ≥1:160) can also be indicative, especially in endemic regions.
While blood culture is the gold standard in the first week, the Widal test is most useful from the second week of illness onwards, when the antibody response becomes robust.

Option A: Leprosy is a bacterial infection caused by Mycobacterium leprae. The Widal test is irrelevant for its diagnosis.
Option C: Rabies is a viral disease affecting the central nervous system. The Widal test, which detects bacterial antibodies, is not used for its diagnosis.
Option D: Poliomyelitis is a viral infection caused by the poliovirus. The Widal test is a bacteriological test and has no role in diagnosing polio.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnostic use of the Widal test for infectious diseases as background academic context rather than a clinical decision trigger.
Nurses must understand the correct timing for specimen collection for the Widal test (after the first week of illness) to avoid false-negative results and ensure accurate diagnosis.
Patient education is crucial. The nurse should explain that a single Widal test may not be conclusive and a second sample might be needed 7-10 days later to confirm the diagnosis by observing a rising antibody titer.
It is important to note that the Widal test has limitations, including false positives due to prior vaccination or cross-reactivity with other infections, and false negatives if performed too early or after antibiotic use.

How to Approach the Question

Identify the core of the question, which asks to link a specific diagnostic test (Widal test) to a particular disease.
This is a factual recall question. Access your knowledge about common laboratory diagnostic tests for major infectious diseases.
Recall that the Widal test is a classic serological test associated with Salmonella infections.
Evaluate the options provided. Typhoid fever is caused by Salmonella typhi.
Eliminate the other options by recalling their distinct diagnostic methods: Leprosy (slit-skin smear/biopsy), Rabies (PCR/clinical signs), and Poliomyelitis (stool culture/PCR).
This process of elimination confirms that the Widal test is correctly matched with Typhoid.

Concept Tested & Keywords

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