Question

What do you understand by Widal test? Describe.

Hint:

Recall that the Widal test diagnoses typhoid via antigen-antibody agglutination.

Answer 1

Step 1: What it Detects:
The Widal test is a serological (blood-based) diagnostic test used to detect typhoid fever, which is caused by the bacterium Salmonella typhi.

Step 2: How it Works:
It is based on the antigen-antibody agglutination reaction: the patient's blood serum is mixed with known O and H antigens of Salmonella typhi; if the patient has been infected, their serum contains specific antibodies (agglutinins) that bind and visibly clump (agglutinate) these antigens, and the pattern/titre of agglutination indicates the presence and stage of typhoid infection.