(Dobrovolskaya, 1971;Daugharty et al., 1972;Brown and O'Leary, 1973;Urquhart, 1974;Buchner et al., 1976). The present study aimed to show the frequency with which sucrose density gradient ultracentrifugation followed by haemagglutination inhibition (HI) could detect specific serum IgM antibodies in patients recently infected with influenza A. The results obtained by this technique were compared with the standard complement fixation test. Material and methods VIRUSThe virus used in all haemagglutination-inhibition tests was A/Port Chalmers/1/73 (A/PC/73) which was propagated in fertile hens' eggs.

Sucrose density gradient ultracentrifugation can be used to detect specific 19S antibodies of the IgM class in the sera of patients recently infected with influenza A virus, provided steps are taken to remove non-specific inhibitors of haemagglutination. The usefulness of the procedure for the diagnosis of influenza requires further evaluation.