Use of the single radial diffusion technique for influenza antibody surveys

A survey of antibody to the influenza A/Hong Kong/1/68 (H3N2) and the variant A/England/42/72 (H3N2) was carried out by two methods, haemagglutination-inhibition (HI) and single radial diffusion (SRD). A comparison of the sensitivity of the two tests indicated that the proportion of sera that produced a zone of 2.5 mm or larger in the SRD tests was equivalent to the proportion that gave HI titres of 1: 40 or more. The test was carried out on serum samples collected from various regions of England. The results showed that approximately 70% had antibody to the A/HK/1/68 virus and only 35% had antibody to A/England/42/72. The SRD test was shown to have several practical advantages for seroepidemiological studies.