Application of the passive haemolysis test for the determination of rubella virus antibodies

A passive haemolysis test for the determination of antibodies against rubella virus haemagglutinin is presented. According to this method, the principle of radial immunodiffusion techinque is applied. Rubella haemagglutinin-coated chick erythrocytes in the agarose gel were lysed by the diffusing positive sera of complement at 37 degrees C. The passive haemolysis test was compared with the conventional haemagglutination inhibition method, and the diameter of the haemolysis zones was shown to be a direct measure of the quantity of antibody added to the well. A plot of the log (HI titre) against the zone diameter gives a straight line. There is no need to remove nonspecific haemagglutination inhibitors. However, all serum samples must be inactivated at 56 degrees C for 30 minutes before testing. Tests of 200 serum samples from healthy women showed a good correlation between the haemagglutination inhibition titre and the antibody titre determined by the passive haemolysis technique. Twenty-one samples with a haemagglutination inhibition titre less than 10 were also negative in the passive haemolysis test. With the exception of one, all sera with a positive haemagglutination inhibition titre showed a positive haemolysis reaction. The method was found to be as specific and as sensitive as the haemagglutination inhibition test. In addition, the technique is rapid and simple for quantitative studies of antibodies against rubella virus.