Evaluation of an immunodiffusion test for screening of rubella immunity.

Rubella antigen obtained by treatment with a mild neutral detergent (Brij-58) of rubella virus infected SIRC cells gave two lines of precipitate in a modified Ouchterlony test (ID), using sera collected during convalescence after rubella. One strong line was obtained with positive sera and sometimes one thin line as well. The presence of at least one line was taken as indicator of rubella immunity. The pattern in which reagents were arranged allowed all positive serum samples to give precipitates showing antibody identity with a rubella control precipitate. Among women in the fertile age screened for immunity, 75% gave precipitates by the ID test and thus were considered to be immune. This should be compared with the 85% positivity found by means of the haemagglutination-inhibition (HI) test. As the HI test occasionally gives false results due to non-removable, non-specific inhibitors, the ID test on basis of the specificity seems to be well suited to be used as a method for the selection of individuals to be vaccinated against rubella.