Microneutralization assay in the diagnosis of influenza infection

Abstract Serology plays an important role in the diagnosis of influenza, particularly in the detection of post-vaccination and post-infection antibodies. When considering the range of diagnostic options, the serological method should be selected depending on the circumstances - whether single or paired serum samples are tested, whether adequate patient medical history data are available, whether epidemiological links are suspected, and, in particular, to what purpose the result will be used (differential diagnosis, post-infection follow-up, post-vaccination monitoring, etc.). The virus neutralization assay is one of the most sensitive and most objective serological tests, but it is highly dependent on the reaction balance and quality of the virus used. Determining the protective titer is crucial for the routine practice. Based on our experiments, we concluded that the virus neutralizing antibody titers are up to eight times as high in comparison with the hemaglutination inhibition test (HIT) or complement fixation reaction (CFR), but the correlation varies and is significantly influenced by interindividual variation in anti-neuraminidase antibodies and those against some internal proteins of influenza virus. We assume that the protective titer in the virus neutralization assay will be not less than 1:80. The predictive value of the titers below 1:40 is questionable.