Why in the news?

Patients with fever in India often undergo testing and treatment for typhoid fever, primarily relying on the Widal test.

• The Widal test, though widely used, has several limitations that affect its accuracy and reliability.

Typhoid diagnosis using Widal Test

• The Widal test is used primarily to diagnose typhoid fever.
• Typhoid fever, caused by Salmonella Typhi and related bacteria, presents with symptoms like high fever, stomach pain, weakness, and gastrointestinal issues.
• It detects antibodies in the patient’s blood against the O (somatic) and H (flagellar) antigens of Salmonella Typhi.
• Procedure:

1. The presence of these antibodies is detected through an agglutination reaction.
2. The test involves serial dilution of the patient’s serum.
3. The highest dilution at which agglutination occurs indicates the antibody titer, with higher titers suggesting an active infection.

Diagnostic Challenges:

• The gold standard for diagnosing typhoid involves isolating the bacteria from blood or bone marrow cultures, which is time-consuming and resource-intensive.
• Widal test is commonly used due to its convenience and accessibility. However, the Widal test’s interpretation is complicated by factors like the need for multiple serum samples, variations in cutoff values, and potential cross-reactivity with antibodies from other infections or vaccines.

Challenges with Widal Test:

• Impractical: A single positive Widal test does not confirm typhoid.
• Complicated result interpretation: High background antibody levels and variability in test cutoff values.
• Cross-reactivity with antibodies from other infections and false negatives due to prior antibiotic therapy undermine test reliability.

Consequences of Widal Test Use:

• Erroneous results obscure the true burden of typhoid in India, leading to inappropriate treatment and financial strain on patients.
• Overuse of antibiotics based on Widal test results contributes to antimicrobial resistance, exacerbating the challenge of treating typhoid.

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