[Determination of antibody avidity using passive hemagglutination reaction].

The antibody avidity index is suggested for the assessment of antibody avidity, that is calculated according to the formula: (T4:T56) x (T4:T37) x (T4:T21), where Tn is the reverse value of antibody titer in the passive hemagglutination test with the same serum at various incubation temperatures. The interpretation of various values of the index is explained, both for the determination of antibody avidity level and for the diagnosis of infectious diseases.