Federer reaction

The Federer reaction is an agglutination test using standard fluids of known typhoid bacteria H (flagellate) and O (bacteria) and type A (A) and type B (B) Salmonella typhi and patient serum for typhoid fever. Assisted diagnosis of typhoid or immunoagglutination experiments for epidemiological investigations. Typhoid and paratyphoid patients can produce specific antibodies in their serum 12 days after their onset, and gradually rise to a peak at 4 weeks and then gradually decrease. After the body is infected with typhoid or paratyphoid, corresponding antibodies will be produced. Normal people due to recessive infection or vaccination, the serum may contain a certain amount of antibodies. Generally when H≥1: 160, O≥1: 80, paratyphoid agglutination value ≥1: 80, it has diagnostic significance. The course of the disease should be reviewed once a week. If the agglutination prices of patients H and O are higher than the reference value or more than four times higher than the original agglutination price, the possibility of typhoid fever is very high. If the H agglutination value is high and O is lower than the normal value, it may be the result of past vaccination or non-specific recall response.

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