Single radial complement fixation test using NP-containing plates: a simple and sensitive method for the detection of influenza infection.

The single radial complement fixation (SRCF) test using nucleoprotein (NP) was compared with the haemagglutination inhibition (HAI) test in the course of the evaluation of the protective efficacy of influenza vaccine. In the case of persons who were not vaccinated, the percent incidence of infection was almost the same (which confirmed by HAI test or by SRCF test), whereas in the case of vaccinees, there was a significant difference between the incidence confirmed by HAI (7.9%) and SRCF (19.4%) tests. The SRCF test was shown to be a simple and sensitive method for detection of a significant rise in antibody titre against influenza virus.