True statement about widal test in typhoid is:

Ans. is 'c' i.e., Previous infection alters widal test (Ref: Ananthanarayan, 9th/e, p. 298 and 9th/e, p. 296-297)People who have had prior infection or immunization may develop an anamnestic response during unrelated fever and may show false positive reaction. This may be differentiated by repetition of test after a week. The anamnestic response shows only a transient rise, while in enteric fever the rise is sustained.About Other Options:Antibiotic (Chloramphenicol) treated cases may show a poor agglutinin response.Other than a positive culture, no specific laboratory test is diagnostic. QBoth prior vaccination (immunization) or infection can alter the widal test.