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What is the interpretation if all the values of Widal test are raised?

Thursday, 17 December 2009
Answered by: Dr Anuj Sharma
World Health Organization, Country Office for India, New Delhi
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Q. What is the interpretation if all values i.e. TO, TH, AH and BH agglutinins are raised?

A.  Interpretation of Widal test is difficult though it is one of the most over-utilized diagnostic tests for typhoid fever in developing countries. The Widal test looks for the presence of somatic (O) and flagellar (H) agglutinins to the enteric fever group of salmonella - Salmonella typhi, Salmonella paratyphi A and Salmonella paratyphi B in the patient's serum. These organisms have now been reclassified as Salmonella enterica serotype Typhi, Salmonella enterica serotype Paratyphi A and Salmonella enterica serotype Paratyphi B.

If all agglutinins (TO, TH, AH, BH) are raised, it is most likely due to previous vaccination or an anamnestic reaction - seen in individuals who have suffered from enteric fever in the past, and develop anti-Salmonella antibodies (agglutinins) during an unrelated or closely related infection due to nonenteric-fever salmonella infections, infections due to other enterobacteriaceae, malaria, dengue, typhus, or immunological disorders. These can be differentiated from true infection by repeat testing after a week or 10 days, which will show no rise in titre. Theoretically, another reason for raised agglutinins could be recurrent or repeated infections due to different salmonella from the enteric fever group, but this is extremely unlikely, especially in the absence of symptoms.

However, please note that all laboratory results should be correlated with clinical findings to avoid misinterpretation.

A.  Interpretation of Widal test is difficult though it is one of the most over-utilized diagnostic tests for typhoid fever in developing countries. The Widal test looks for the presence of somatic (O) and flagellar (H) agglutinins to the enteric fever group of salmonella - Salmonella typhi, Salmonella paratyphi A and Salmonella paratyphi B in the patient's serum. These organisms have now been reclassified as Salmonella enterica serotype Typhi, Salmonella enterica serotype Paratyphi A and Salmonella enterica serotype Paratyphi B.

If all agglutinins (TO, TH, AH, BH) are raised, it is most likely due to previous vaccination or an anamnestic reaction - seen in individuals who have suffered from enteric fever in the past, and develop anti-Salmonella antibodies (agglutinins) during an unrelated or closely related infection due to nonenteric-fever salmonella infections, infections due to other enterobacteriaceae, malaria, dengue, typhus, or immunological disorders. These can be differentiated from true infection by repeat testing after a week or 10 days, which will show no rise in titre. Theoretically, another reason for raised agglutinins could be recurrent or repeated infections due to different salmonella from the enteric fever group, but this is extremely unlikely, especially in the absence of symptoms.

However, please note that all laboratory results should be correlated with clinical findings to avoid misinterpretation.

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