Evaluation of candidate international reference methods for the rubella hemagglutination inhibition test: report of a collaborative study.

Rubella virus infection in children or adults results in a self-limited, benign disease characterized by mild upper respiratory symptoms, an erythematous rash, and suboccipital lymphadenopathy. Complications of arthralgia and arthritis which may follow disappearance of the rash are most common in young women. Severe complications occur rarely. Infection of the fetus during the first trimester of pregnancy and, to a lesser degree, in the second and third tri.mesters may result in congenital rubella, a frequent cause of malformations and disabilities (I, 2). Of the various serologic methods for detecting or measuring rubella antibodies, the hemagglutination-inhibition (HI) test has had the widest use and has been evaluated the most frequently. When the test is performed properly, the indicated presence of antibodies correlates well with resistance to developing rubella. The test can be used to determine which individuals need vaccination and which pregnant women are at risk of giving birth to an infant with congenital rubella. However, the test does not distinguish between IgM and IgC antibody, and in order to determine whether a positive test reflects a recent infection, a test for IgM antibody is necessary. The basic principles of all the modifications of the HI test are as originally described (3). In addition, attempts have been made to standardize the HI procedure. In the United States, the Centers for Disease Control (CDC) and National Committee for Clinical Laboratory Standards (NCCLS) have published standardized HI procedures (4, 5).