Which of the following is true about the antigen titre in Widal test?

H-antigen titre remains positive for several months & reaction to it is rapid. Option 1, 3 - O Abs appear early and disappear early and indicate recent infection. H Abs appear late and disappear late. Option 2 Widal test: it can be done in second week and third week. Principle: It is an agglutination test where H and O antibodies are detected in the patient's sera by using H and O Antigens. Antigens used: Four antigens are used: O antigen of S.Typhi (TO) H antigens of S.Typhi (TH) S.Paratyphi A (AH) S.Paratyphi B (BH) - H agglutinins persist longer than O agglutinins. Four-fold rise in antibody titre in paired sera at 1 week interval is more meaningful than a single high titre. - After 1 week if titre rises- indicates true infection. - After 1 week if titre falls- indicates anamnestic responses.