True statement about widal test in typhoid is-(

Ans. is 'c' i.e., Previous infection alters widal test . Person 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 : . Cases treated with antibiotic (cholermphenicol) may show a poor agglutinin response. . Other than a positive culture, no specific laboratory test is diagnostic - . Both prior vaccination (immunization) or infection can alter the widal test (see above).