Description
The Widal test measures the capacity of antibodies against LPS and flagella in the serum of individuals with suspected typhoid fever to agglutinate cells of S. Typhi; the test was introduced over a century ago and it is still widely used [20]. It is simple, inexpensive, and takes only a few minutes.
When Widal test is positive?
The Widal test is positive if TO antigen titer is more than 1:160 in an active infection, or if TH antigen titer is more than 1:160 in past infection or in immunized persons. A single Widal test is of little clinical relevance especially in endemic areas such as Indian subcontinent, Africa and South-east Asia.
What is normal Widal test?
Conclusion: In case of singular Widal test, baseline values for the normal range was found to be 1:20 – 1:80 for all the antigens (TO, TH, AO, AH, BO, BH), except BH, for which it was 1:20-1:40.
What does Widal test measure?
The Widal test has been in use for more than a century as an aid in the diagnosis of typhoid fever (7, 26). It is a tube dilution test which measures agglutinating antibodies against the lipopolysaccharide O and protein flagellar H antigens of S. typhi.
What is widal test negative?
So a negative Widal test result has a good predictive value for the absence of the disease but a positive result would have a low predictive value for the presence of typhoid fever.
How is widal test done?
The main principle of widal test is that if homologous antibody is present in patients serum, it will react with respective antigen in the reagent and gives visible clumping on the test card and agglutination in the tube. The antigens used in the test are “H” and “O” antigens of Salmonella Typhi and “H” antigen of S.
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