WIDAL TEST TITRE

The baseline titre for antibodies to “O” and “H” antigens of Salmonella enterica serotype typhi is 1:40 and hence cutoff level is ≥1:80 for a single antibody test titre. The baseline titre for antibody to H antigen of Salmonella enterica serotype paratyphiA and paratyphi B is 1:80 and the cutoff level is ≥1:160 for a single antibody test titre. Rising titres on repitition of test after few days is more suggestive of enteric fever.
LIMITATIONS OF WIDAL TEST:
Numerous false positives due to cross reacting antibodies and heterospecific anamnestic responses and false low titres as a result of partial treatment are observed. This makes clinical correlation with lab findings mandatory.