Experience with a rubella proficiency testing program in New York State, 1971-1974

Demonstration of rubella antibody has become, in recent years, one of the tests most frequently requested of virus diagnostic laboratories. The hemagglutination inhibition (HI) technique described in 1967 by Stewart et al is sensitive, reproducible, convenient, and economic and commercial availability of diagnostic kits enables laboratories to offer this test without costly facilities for maintenance of cell cultures, preparation of antigen, etc. Recognizing the need for a standardized procedure for the rubella HI test, the United States Public Health Service appointed a committee to evaluate the reproducibility and sensitivity of the various procedures in current use. A report published in 1970 recommended that nonspecific inhibitors be removed by the use of manganese chloride and heparin or, as an 'acceptable alternative' by the calcium chloride dextran sulfate method. Fresh red blood cells from 1 to 3 day old unfed chicks or from geese were chosen as the erythrocytes for the test. In 1971, however, most laboratories in New York State did not follow this procedure, which has not been mandated by federal or state laws or regulations. The majority used the kaolin method for removal of inhibitors; only a few laboratories used the specified erythrocytes. This paper describes the implementation of the New York State rubella proficiency testing program and the experience gained during the first 4 yr of its operation.