Widal Test (Tube Agglutination)
Understanding Widal Test (Tube Agglutination)
What is Widal Test (Tube Agglutination)?
The widal test (Tube agglutination) is a blood test that detects enteric fever – Typhoid and Paratyphoid fever. Enteric fever is a systemic infection caused by bacteria, usually through ingestion of contaminated food or water. The symptoms of typhoid fever include high fever, diarrhea, headache, constipation, and stomach pain.
Widal test detects antibodies (agglutinins) in a blood sample against two antigens (O & H) of bacteria Salmonella enterica. In some cases where culturing facilities are not available, this test is reliable and can add value in the diagnosis of typhoid fever. Typhoid fever can be treated with antibiotics, while vaccination is also useful in the prevention of the disease.
What is Widal Test (Tube Agglutination) used for?
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To diagnose Enteric fever (Typhoid and Paratyphoid fever)
Interpreting Widal Test (Tube Agglutination) results
Interpretations
If the antibody against Salmonella is present in patient’s serum, it will react with the respective antigen in the reagent and give visible agglutination (clumping) at the bottom of the test tube after 18 hrs.
The highest dilution of the patient’s serum sample that gives a visible agglutination with the Widal test antigen suspensions is the antibody titre.
The serum sample which shows the titre of 1:80 or more for O agglutination and 1:160 or more for H agglutination indicates active infection. A rise in titres (4-fold or more) in the two blood samples taken 10 days apart confirms the diagnosis. Please note that different labs may have different reference values for the interpretation of the Widal test.
The interpretation of a Widal test is greatly influenced by the nature and extent of the patient’s previous contact with typhoid antigens. It can be either due to clinical or subclinical infection with typhoid or related organisms or from typhoid vaccination. The lesser the extent of the previous contact, the greater is the usefulness of the Widal test.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Widal Test (Tube Agglutination)
Frequently Asked Questions about Widal Test (Tube Agglutination)
Q. Is there any preparation required before the test?
Q. What are the different methods for performing Widal test?
Q. Is there any risk associated with this test?
Q. What are the limitations of Widal test?
Q. What are the other tests to diagnose Enteric fever?
Q. How can you prevent typhoid fever?
Q. What is the appropriate time during illness for performing Widal test?
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